Engine specific parameters - Amazon ElastiCache
Valkey and Redis OSS parametersMemcached specific parameters

Engine specific parameters

Valkey and Redis OSS

Most Valkey 8 parameters are compatible with Redis OSS 7.1 parameters. Valkey 7.2 parameters are the same as Redis OSS 7 parameters.

If you do not specify a parameter group for your Valkey or Redis OSS cluster, then a default parameter group appropriate to your engine version will be used. You can't change the values of any parameters in the default parameter group. However, you can create a custom parameter group and assign it to your cluster at any time as long as the values of conditionally modifiable parameters are the same in both parameter groups. For more information, see Creating an ElastiCache parameter group.

Valkey and Redis OSS parameters

Valkey 8 parameter changes

Parameter group family: valkey8

Note

Redis OSS 7.2.4 is incompatible with Valkey 8 parameter groups.

Specific parameter changes
Name Details Description

repl-backlog-size

Default: 10485760

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

The size, in bytes, of the primary node backlog buffer. The backlog is used for recording updates to data at the primary node. When a read replica connects to the primary, it attempts to perform a partial sync (psync), where it applies data from the backlog to catch up with the primary node. If the psync fails, then a full sync is required.

The minimum value for this parameter is 16384.

Note: Beginning with Redis OSS 2.8.22, this parameter applies to the primary cluster as well as the read replicas.

maxmemory-samples

Default: 3

Permitted values: 1 to 64

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

For least-recently-used (LRU) and time-to-live (TTL) calculations, this parameter represents the sample size of keys to check. By default, Redis OSS chooses 3 keys and uses the one that was used least recently.
New parameter groups
Name Details Description

extended-redis-compatibility

Permitted values: yes, no

Default: yes

Type: boolean

Modifiable: Yes

Changes take place: immediately

Extended Redis OSS compatibility mode makes Valkey pretend to be Redis OSS 7.2. Enable this only if you have problems with tools or clients.

Customer-facing impacts:

  • LOADING - Redis OSS is loading the dataset in memory

  • BUSY - Redis OSS is busy

  • MISCONF - Redis OSS is configured in either of these ways:

    • The HELLO command returns "server" => "redis" and "version" => "7.2.4" (our Redis OSS compatibility version).

    • The INFO field for mode is called "redis_mode".
Removed parameter groups
Name Details Description

lazyfree-lazy-eviction

Permitted values: yes, no

Default: no

Type: boolean

Modifiable: Yes

Changes take place: immediately

Performs an asynchronous delete on evictions.

lazyfree-lazy-expire

Permitted values: yes, no

Default: no

Type: boolean

Modifiable: Yes

Changes take place: immediately

Performs an asynchronous delete on expired keys.

lazyfree-lazy-server-del

Permitted values: yes, no

Default: no

Type: boolean

Modifiable: Yes

Changes take place: immediately

Performs an asynchronous delete for commands which update values.

lazyfree-lazy-user-del

Default: no

Type: string

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster

When the value is set to yes, the DEL command acts the same as UNLINK.

replica-lazy-flush

Default: yes

Type: boolean

Modifiable: No

Former name: slave-lazy-flush

Performs an asynchronous flushDB during replica sync.

Valkey 7.2 and Redis OSS 7 parameter changes

Parameter group family: valkey7

Valkey 7.2 default parameter groups are as follows:

  • default.valkey7 – Use this parameter group, or one derived from it, for Valkey (cluster mode disabled) clusters and replication groups.

  • default.valkey7.cluster.on – Use this parameter group, or one derived from it, for Valkey (cluster mode enabled) clusters and replication groups.

Parameter group family: redis7

Redis OSS 7 default parameter groups are as follows:

  • default.redis7 – Use this parameter group, or one derived from it, for Redis OSS (cluster mode disabled) clusters and replication groups.

  • default.redis7.cluster.on – Use this parameter group, or one derived from it, for Redis OSS (cluster mode enabled) clusters and replication groups.

Specific parameter changes

Parameters added in Redis OSS 7 are as follows. Valkey 7.2 also supports these parameters.

Name Details Description
cluster-allow-pubsubshard-when-down

Permitted values: yes, no

Default: yes

Type: string

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

When set to the default of yes, allows nodes to serve pubsub shard traffic while the cluster is in a down state, as long as it believes it owns the slots.
cluster-preferred-endpoint-type

Permitted values: ip, tls-dynamic

Default: tls-dynamic

Type: string

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

This value controls what endpoint is returned for MOVED/ASKING requests as well as the endpoint field for CLUSTER SLOTS and CLUSTER SHARDS. When the value is set to ip, the node will advertise its ip address. When the value is set to tls-dynamic, the node will advertise a hostname when encryption-in-transit is enabled and an ip address otherwise.
latency-tracking

Permitted values: yes, no

Default: no

Type: string

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

When set to yes tracks the per command latencies and enables exporting the percentile distribution via the INFO latency statistics command, and cumulative latency distributions (histograms) via the LATENCY command.
hash-max-listpack-entries

Permitted values: 0+

Default: 512

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

The maximum number of hash entries in order for the dataset to be compressed.
hash-max-listpack-value

Permitted values: 0+

Default: 64

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

The threshold of biggest hash entries in order for the dataset to be compressed.
zset-max-listpack-entries

Permitted values: 0+

Default: 128

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

The maximum number of sorted set entries in order for the dataset to be compressed.
zset-max-listpack-value

Permitted values: 0+

Default: 64

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

The threshold of biggest sorted set entries in order for the dataset to be compressed.

Parameters changed in Redis OSS 7 are as follows.

Name Details Description
activerehashing

Modifiable: no. In Redis OSS 7, this parameter is hidden and enabled by default. In order to disable it, you need to create a support case.

Modifiable was yes.

Parameters removed in Redis OSS 7 are as follows.

Name Details Description
hash-max-ziplist-entries

Permitted values: 0+

Default: 512

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

Use listpack instead of ziplist for representing small hash encoding
hash-max-ziplist-value

Permitted values: 0+

Default: 64

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

Use listpack instead of ziplist for representing small hash encoding
zset-max-ziplist-entries

Permitted values: 0+

Default: 128

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

Use listpack instead of ziplist for representing small hash encoding.
zset-max-ziplist-value

Permitted values: 0+

Default: 64

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

Use listpack instead of ziplist for representing small hash encoding.
list-max-ziplist-size

Permitted values:

Default: -2

Type: integer

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster.

The number of entries allowed per internal list node.

Redis OSS 6.x parameter changes

Parameter group family: redis6.x

Redis OSS 6.x default parameter groups are as follows:

  • default.redis6.x – Use this parameter group, or one derived from it, for Valkey or Redis OSS (cluster mode disabled) clusters and replication groups.

  • default.redis6.x.cluster.on – Use this parameter group, or one derived from it, for Valkey or Redis OSS (cluster mode enabled) clusters and replication groups.

Note

In Redis OSS engine version 6.2, when the r6gd node family was introduced for use with Data tiering in ElastiCache, only noeviction, volatile-lru and allkeys-lru max-memory policies are supported with r6gd node types.

For more information, see ElastiCache (Redis OSS) version 6.2 (enhanced) and ElastiCache (Redis OSS) version 6.0 (enhanced).

Parameters added in Redis OSS 6.x are as follows.

Details Description
acl-pubsub-default (added in 6.2)

Permitted values: resetchannels, allchannels

Default: allchannels

Type: string

Modifiable: Yes

Changes take effect: The existing Redis OSS users associated to the cluster will continue to have existing permissions. Either update the users or reboot the cluster to update the existing Redis OSS users.

Default pubsub channel permissions for ACL users deployed to this cluster.

cluster-allow-reads-when-down (added in 6.0)

Default: no

Type: string

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster

When set to yes, a Redis OSS (cluster mode enabled) replication group continues to process read commands even when a node is not able to reach a quorum of primaries.

When set to the default of no, the replication group rejects all commands. We recommend setting this value to yes if you are using a cluster with fewer than three node groups or your application can safely handle stale reads.

tracking-table-max-keys (added in 6.0)

Default: 1,000,000

Type: number

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster

To assist client-side caching, Redis OSS supports tracking which clients have accessed which keys.

When the tracked key is modified, invalidation messages are sent to all clients to notify them their cached values are no longer valid. This value enables you to specify the upper bound of this table. After this parameter value is exceeded, clients are sent invalidation randomly. This value should be tuned to limit memory usage while still keeping track of enough keys. Keys are also invalidated under low memory conditions.

acllog-max-len (added in 6.0)

Default: 128

Type: number

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster

This value corresponds to the max number of entries in the ACL log.

active-expire-effort (added in 6.0)

Default: 1

Type: number

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster

Redis OSS deletes keys that have exceeded their time to live by two mechanisms. In one, a key is accessed and is found to be expired. In the other, a periodic job samples keys and causes those that have exceeded their time to live to expire. This parameter defines the amount of effort that Redis OSS uses to expire items in the periodic job.

The default value of 1 tries to avoid having more than 10 percent of expired keys still in memory. It also tries to avoid consuming more than 25 percent of total memory and to add latency to the system. You can increase this value up to 10 to increase the amount of effort spent on expiring keys. The tradeoff is higher CPU and potentially higher latency. We recommend a value of 1 unless you are seeing high memory usage and can tolerate an increase in CPU utilization.

lazyfree-lazy-user-del (added in 6.0)

Default: no

Type: string

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster

When the value is set to yes, the DEL command acts the same as UNLINK.

Parameters removed in Redis OSS 6.x are as follows.

Name Details Description
lua-replicate-commands

Permitted values: yes/no

Default: yes

Type: boolean

Modifiable: Yes

Changes take effect: Immediately

 Always enable Lua effect replication or not in Lua scripts

Redis OSS 5.0.3 parameter changes

Parameter group family: redis5.0

Redis OSS 5.0 default parameter groups

  • default.redis5.0 – Use this parameter group, or one derived from it, for Valkey or Redis OSS (cluster mode disabled) clusters and replication groups.

  • default.redis5.0.cluster.on – Use this parameter group, or one derived from it, for Valkey or Redis OSS (cluster mode enabled) clusters and replication groups.

Parameters added in Redis OSS 5.0.3
Name Details Description
rename-commands

Default: none

Type: string

Modifiable: Yes

Changes take effect: Immediately across all nodes in the cluster

 A space-separated list of renamed Redis OSS commands. The following is a restricted list of commands available for renaming:

APPEND AUTH BITCOUNT BITFIELD BITOP BITPOS BLPOP BRPOP BRPOPLPUSH BZPOPMIN BZPOPMAX CLIENT CLUSTER COMMAND DBSIZE DECR DECRBY DEL DISCARD DUMP ECHO EVAL EVALSHA EXEC EXISTS EXPIRE EXPIREAT FLUSHALL FLUSHDB GEOADD GEOHASH GEOPOS GEODIST GEORADIUS GEORADIUSBYMEMBER GET GETBIT GETRANGE GETSET HDEL HEXISTS HGET HGETALL HINCRBY HINCRBYFLOAT HKEYS HLEN HMGET HMSET HSET HSETNX HSTRLEN HVALS INCR INCRBY INCRBYFLOAT INFO KEYS LASTSAVE LINDEX LINSERT LLEN LPOP LPUSH LPUSHX LRANGE LREM LSET LTRIM MEMORY MGET MONITOR MOVE MSET MSETNX MULTI OBJECT PERSIST PEXPIRE PEXPIREAT PFADD PFCOUNT PFMERGE PING PSETEX PSUBSCRIBE PUBSUB PTTL PUBLISH PUNSUBSCRIBE RANDOMKEY READONLY READWRITE RENAME RENAMENX RESTORE ROLE RPOP RPOPLPUSH RPUSH RPUSHX SADD SCARD SCRIPT SDIFF SDIFFSTORE SELECT SET SETBIT SETEX SETNX SETRANGE SINTER SINTERSTORE SISMEMBER SLOWLOG SMEMBERS SMOVE SORT SPOP SRANDMEMBER SREM STRLEN SUBSCRIBE SUNION SUNIONSTORE SWAPDB TIME TOUCH TTL TYPE UNSUBSCRIBE UNLINK UNWATCH WAIT WATCH ZADD ZCARD ZCOUNT ZINCRBY ZINTERSTORE ZLEXCOUNT ZPOPMAX ZPOPMIN ZRANGE ZRANGEBYLEX ZREVRANGEBYLEX ZRANGEBYSCORE ZRANK ZREM ZREMRANGEBYLEX ZREMRANGEBYRANK ZREMRANGEBYSCORE ZREVRANGE ZREVRANGEBYSCORE ZREVRANK ZSCORE ZUNIONSTORE SCAN SSCAN HSCAN ZSCAN XINFO XADD XTRIM XDEL XRANGE XREVRANGE XLEN XREAD XGROUP XREADGROUP XACK XCLAIM XPENDING GEORADIUS_RO GEORADIUSBYMEMBER_RO LOLWUT XSETID SUBSTR

For more information, see ElastiCache (Redis OSS) version 5.0.6 (enhanced).

Redis OSS 5.0.0 parameter changes

Parameter group family: redis5.0

Redis OSS 5.0 default parameter groups

  • default.redis5.0 – Use this parameter group, or one derived from it, for Valkey or Redis OSS (cluster mode disabled) clusters and replication groups.

  • default.redis5.0.cluster.on – Use this parameter group, or one derived from it, for Valkey or Redis OSS (cluster mode enabled) clusters and replication groups.

Parameters added in Redis OSS 5.0
Name Details Description
stream-node-max-bytes

Permitted values: 0+

Default: 4096

Type: integer

Modifiable: Yes

Changes take effect: Immediately

 The stream data structure is a radix tree of nodes that encode multiple items inside. Use this configuration to specify the maximum size of a single node in radix tree in Bytes. If set to 0, the size of the tree node is unlimited.
stream-node-max-entries

Permitted values: 0+

Default: 100

Type: integer

Modifiable: Yes

Changes take effect: Immediately

 The stream data structure is a radix tree of nodes that encode multiple items inside. Use this configuration to specify the maximum number of items a single node can contain before switching to a new node when appending new stream entries. If set to 0, the number of items in the tree node is unlimited
active-defrag-max-scan-fields

Permitted values: 1 to 1000000

Default: 1000

Type: integer

Modifiable: Yes

Changes take effect: Immediately

 Maximum number of set/hash/zset/list fields that will be processed from the main dictionary scan
lua-replicate-commands

Permitted values: yes/no

Default: yes

Type: boolean

Modifiable: Yes

Changes take effect: Immediately

 Always enable Lua effect replication or not in Lua scripts
replica-ignore-maxmemory

Default: yes

Type: boolean

Modifiable: No

 Determines if replica ignores maxmemory setting by not evicting items independent from the primary

Redis OSS has renamed several parameters in engine version 5.0 in response to community feedback. For more information, see What's New in Redis OSS 5?. The following table lists the new names and how they map to previous versions.

Parameters renamed in Redis OSS 5.0
Name Details Description
replica-lazy-flush

Default: yes

Type: boolean

Modifiable: No

Former name: slave-lazy-flush

 Performs an asynchronous flushDB during replica sync.
client-output-buffer-limit-replica-hard-limit

Default: For values see Redis OSS node-type specific parameters

Type: integer

Modifiable: No

Former name: client-output-buffer-limit-slave-hard-limit

 For Redis OSS read replicas: If a client's output buffer reaches the specified number of bytes, the client will be disconnected.
client-output-buffer-limit-replica-soft-limit

Default: For values see Redis OSS node-type specific parameters

Type: integer

Modifiable: No

Former name: client-output-buffer-limit-slave-soft-limit

 For Redis OSS read replicas: If a client's output buffer reaches the specified number of bytes, the client will be disconnected, but only if this condition persists for client-output-buffer-limit-replica-soft-seconds.
client-output-buffer-limit-replica-soft-seconds

Default: 60

Type: integer

Modifiable: No

Former name: client-output-buffer-limit-slave-soft-seconds

 For Redis OSS read replicas: If a client's output buffer remains at client-output-buffer-limit-replica-soft-limit bytes for longer than this number of seconds, the client will be disconnected.
replica-allow-chaining

Default: no

Type: string

Modifiable: No

Former name: slave-allow-chaining

 Determines whether a read replica in Redis OSS can have read replicas of its own.
min-replicas-to-write

Default: 0

Type: integer

Modifiable: Yes

Former name: min-slaves-to-write

Changes Take Effect: Immediately

The minimum number of read replicas which must be available in order for the primary node to accept writes from clients. If the number of available replicas falls below this number, then the primary node will no longer accept write requests.

If either this parameter or min-replicas-max-lag is 0, then the primary node will always accept writes requests, even if no replicas are available.
min-replicas-max-lag

Default: 10

Type: integer

Modifiable: Yes

Former name: min-slaves-max-lag

Changes Take Effect: Immediately

The number of seconds within which the primary node must receive a ping request from a read replica. If this amount of time passes and the primary does not receive a ping, then the replica is no longer considered available. If the number of available replicas drops below min-replicas-to-write, then the primary will stop accepting writes at that point.

If either this parameter or min-replicas-to-write is 0, then the primary node will always accept write requests, even if no replicas are available.
close-on-replica-write

Default: yes

Type: boolean

Modifiable: Yes

Former name: close-on-slave-write

Changes Take Effect: Immediately

If enabled, clients who attempt to write to a read-only replica will be disconnected.
Parameters removed in Redis OSS 5.0
Name Details Description
repl-timeout

Default: 60

Modifiable: No

 Parameter is not available in this version.

Redis OSS 4.0.10 parameter changes

Parameter group family: redis4.0

Redis OSS 4.0.x default parameter groups

  • default.redis4.0 – Use this parameter group, or one derived from it, for Valkey or Redis OSS (cluster mode disabled) clusters and replication groups.

  • default.redis4.0.cluster.on – Use this parameter group, or one derived from it, for Valkey or Redis OSS (cluster mode enabled) clusters and replication groups.

Parameters changed in Redis OSS 4.0.10
Name Details Description
maxmemory-policy

Permitted values: allkeys-lru, volatile-lru, allkeys-lfu, volatile-lfu, allkeys-random, volatile-random, volatile-ttl, noeviction

Default: volatile-lru

Type: string

Modifiable: Yes

Changes take place: immediately

 maxmemory-policy was added in version 2.6.13. In version 4.0.10 two new permitted values are added: allkeys-lfu, which will evict any key using approximated LFU, and volatile-lfu, which will evict using approximated LFU among the keys with an expire set. In version 6.2, when the r6gd node family was introduced for use with data-tiering, only noeviction, volatile-lru and allkeys-lru max-memory policies are supported with r6gd node types.
Parameters added in Redis OSS 4.0.10
Name Details Description
Async deletion parameters
lazyfree-lazy-eviction

Permitted values: yes/no

Default: no

Type: boolean

Modifiable: Yes

Changes take place: immediately

 Performs an asynchronous delete on evictions.
lazyfree-lazy-expire

Permitted values: yes/no

Default: no

Type: boolean

Modifiable: Yes

Changes take place: immediately

 Performs an asynchronous delete on expired keys.
lazyfree-lazy-server-del

Permitted values: yes/no

Default: no

Type: boolean

Modifiable: Yes

Changes take place: immediately

 Performs an asynchronous delete for commands which update values.
slave-lazy-flush

Permitted values: N/A

Default: no

Type: boolean

Modifiable: No

Changes take place: N/A		 Performs an asynchronous flushDB during slave sync.
LFU parameters
lfu-log-factor

Permitted values: any integer > 0

Default: 10

Type: integer

Modifiable: Yes

Changes take place: immediately

 Set the log factor, which determines the number of key hits to saturate the key counter.
lfu-decay-time

Permitted values: any integer

Default: 1

Type: integer

Modifiable: Yes

Changes take place: immediately

 The amount of time in minutes to decrement the key counter.
Active defragmentation parameters
activedefrag

Permitted values: yes/no

Default: no

Type: boolean

Modifiable: Yes

Changes take place: immediately

 Enabled active defragmentation.
active-defrag-ignore-bytes

Permitted values: 10485760-104857600

Default: 104857600

Type: integer

Modifiable: Yes

Changes take place: immediately

 Minimum amount of fragmentation waste to start active defrag.
active-defrag-threshold-lower

Permitted values: 1-100

Default: 10

Type: integer

Modifiable: Yes

Changes take place: immediately

 Minimum percentage of fragmentation to start active defrag.
active-defrag-threshold-upper

Permitted values: 1-100

Default: 100

Type: integer

Modifiable: Yes

Changes take place: immediately

 Maximum percentage of fragmentation at which we use maximum effort.
active-defrag-cycle-min

Permitted values: 1-75

Default: 25

Type: integer

Modifiable: Yes

Changes take place: immediately

 Minimal effort for defrag in CPU percentage.
active-defrag-cycle-max

Permitted values: 1-75

Default: 75

Type: integer

Modifiable: Yes

Changes take place: immediately

 Maximal effort for defrag in CPU percentage.
Client output buffer parameters
client-query-buffer-limit

Permitted values: 1048576-1073741824

Default: 1073741824

Type: integer

Modifiable: Yes

Changes take place: immediately

 Max size of a single client query buffer.
proto-max-bulk-len

Permitted values: 1048576-536870912

Default: 536870912

Type: integer

Modifiable: Yes

Changes take place: immediately

 Max size of a single element request.

Redis OSS 3.2.10 parameter changes

Parameter group family: redis3.2

ElastiCache (Redis OSS) 3.2.10 there are no additional parameters supported.

Redis OSS 3.2.6 parameter changes

Parameter group family: redis3.2

For Redis OSS 3.2.6 there are no additional parameters supported.

Redis OSS 3.2.4 parameter changes

Parameter group family: redis3.2

Beginning with Redis OSS 3.2.4 there are two default parameter groups.

  • default.redis3.2 – When running Redis OSS 3.2.4, specify this parameter group or one derived from it, if you want to create a Valkey or Redis OSS (cluster mode disabled) replication group and still use the additional features of Redis OSS 3.2.4.

  • default.redis3.2.cluster.on – Specify this parameter group or one derived from it, when you want to create a Valkey or Redis OSS (cluster mode enabled) replication group.

New parameters for Redis OSS 3.2.4

Parameter group family: redis3.2

For Redis OSS 3.2.4 the following additional parameters are supported.

Name Details Description
list-max-ziplist-size

Default: -2

Type: integer

Modifiable: No

 Lists are encoded in a special way to save space. The number of entries allowed per internal list node can be specified as a fixed maximum size or a maximum number of elements. For a fixed maximum size, use -5 through -1, meaning:

  • -5: max size: 64 Kb - not recommended for normal workloads

  • -4: max size: 32 Kb - not recommended

  • -3: max size: 16 Kb - not recommended

  • -2: max size: 8 Kb - recommended

  • -1: max size: 4 Kb - recommended

  • Positive numbers mean store up to exactly that number of elements per list node.
list-compress-depth

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Lists may also be compressed. Compress depth is the number of quicklist ziplist nodes from each side of the list to exclude from compression. The head and tail of the list are always uncompressed for fast push and pop operations. Settings are:

  • 0: Disable all compression.

  • 1: Start compressing with the 1st node in from the head and tail.

    [head]->node->node->...->node->[tail]

    All nodes except [head] and [tail] compress.

  • 2: Start compressing with the 2nd node in from the head and tail.

    [head]->[next]->node->node->...->node->[prev]->[tail]

    [head], [next], [prev], [tail] do not compress. All other nodes compress.

  • Etc.
cluster-enabled

Default: no/yes *

Type: string

Modifiable: No

Indicates whether this is a Valkey or Redis OSS (cluster mode enabled) replication group in cluster mode (yes) or a Valkey or Redis OSS (cluster mode enabled) replication group in non-cluster mode (no). Valkey or Redis OSS (cluster mode enabled) replication groups in cluster mode can partition their data across up to 500 node groups.

* Redis OSS 3.2.x has two default parameter groups.

  • default.redis3.2 – default value no.

  • default.redis3.2.cluster.on – default value yes.

.
cluster-require-full-coverage

Default: no

Type: boolean

Modifiable: yes

Changes Take Effect: Immediately

When set to yes, Valkey or Redis OSS (cluster mode enabled) nodes in cluster mode stop accepting queries if they detect there is at least one hash slot uncovered (no available node is serving it). This way if the cluster is partially down, the cluster becomes unavailable. It automatically becomes available again as soon as all the slots are covered again.

However, sometimes you want the subset of the cluster which is working to continue to accept queries for the part of the key space that is still covered. To do so, just set the cluster-require-full-coverage option to no.
hll-sparse-max-bytes

Default: 3000

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

HyperLogLog sparse representation bytes limit. The limit includes the 16 byte header. When a HyperLogLog using the sparse representation crosses this limit, it is converted into the dense representation.

A value greater than 16000 is not recommended, because at that point the dense representation is more memory efficient.

We recommend a value of about 3000 to have the benefits of the space-efficient encoding without slowing down PFADD too much, which is O(N) with the sparse encoding. The value can be raised to ~10000 when CPU is not a concern, but space is, and the data set is composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
reserved-memory-percent

Default: 25

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

The percent of a node's memory reserved for nondata use. By default, the Redis OSS data footprint grows until it consumes all of the node's memory. If this occurs, then node performance will likely suffer due to excessive memory paging. By reserving memory, you can set aside some of the available memory for non-Redis OSS purposes to help reduce the amount of paging.

This parameter is specific to ElastiCache, and is not part of the standard Redis OSS distribution.

For more information, see reserved-memory and Managing reserved memory for Valkey and Redis OSS.

Parameters changed in Redis OSS 3.2.4 (enhanced)

Parameter group family: redis3.2

For Redis OSS 3.2.4 the following parameters were changed.

Name Details Change
activerehashing

Modifiable: Yes if the parameter group is not associated with any cache clusters. Otherwise, no.

Modifiable was No.
databases

Modifiable: Yes if the parameter group is not associated with any cache clusters. Otherwise, no.

Modifiable was No.
appendonly

Default: off

Modifiable: No

If you want to upgrade from an earlier Redis OSS version, you must first turn appendonly off.
appendfsync

Default: off

Modifiable: No

If you want to upgrade from an earlier Redis OSS version, you must first turn appendfsync off.
repl-timeout

Default: 60

Modifiable: No

 Is now unmodifiable with a default of 60.
tcp-keepalive

Default: 300

Default was 0.
list-max-ziplist-entries

Parameter is no longer available.
list-max-ziplist-value

Parameter is no longer available.

Redis OSS 2.8.24 (enhanced) added parameters

Parameter group family: redis2.8

For Redis OSS 2.8.24 there are no additional parameters supported.

Redis OSS 2.8.23 (enhanced) added parameters

Parameter group family: redis2.8

For Redis OSS 2.8.23 the following additional parameter is supported.

Name Details Description
close-on-slave-write

Default: yes

Type: string (yes/no)

Modifiable: Yes

Changes Take Effect: Immediately

If enabled, clients who attempt to write to a read-only replica will be disconnected.

How close-on-slave-write works

The close-on-slave-write parameter is introduced by Amazon ElastiCache to give you more control over how your cluster responds when a primary node and a read replica node swap roles due to promoting a read replica to primary.

Image: close-on-replica-write, everything working fine

If the read-replica cluster is promoted to primary for any reason other than a Multi-AZ enabled replication group failing over, the client will continue trying to write to endpoint A. Because endpoint A is now the endpoint for a read-replica, these writes will fail. This is the behavior for Redis OSS before ElastiCache introducing close-on-replica-write and the behavior if you disable close-on-replica-write.

Image: close-on-slave-write, writes failing

With close-on-replica-write enabled, any time a client attempts to write to a read-replica, the client connection to the cluster is closed. Your application logic should detect the disconnection, check the DNS table, and reconnect to the primary endpoint, which now would be endpoint B.

Image: close-on-slave-write, writing to new primary cluster

When you might disable close-on-replica-write

If disabling close-on-replica-write results in writes to the failing cluster, why disable close-on-replica-write?

As previously mentioned, with close-on-replica-write enabled, any time a client attempts to write to a read-replica the client connection to the cluster is closed. Establishing a new connection to the node takes time. Thus, disconnecting and reconnecting as a result of a write request to the replica also affects the latency of read requests that are served through the same connection. This effect remains in place until a new connection is established. If your application is especially read-heavy or very latency-sensitive, you might keep your clients connected to avoid degrading read performance.

Redis OSS 2.8.22 (enhanced) added parameters

Parameter group family: redis2.8

For Redis OSS 2.8.22 there are no additional parameters supported.

Important

  • Beginning with Redis OSS version 2.8.22, repl-backlog-size applies to the primary cluster as well as to replica clusters.

  • Beginning with Redis OSS version 2.8.22, the repl-timeout parameter is not supported. If it is changed, ElastiCache will overwrite with the default (60s), as we do with appendonly.

The following parameters are no longer supported.

  • appendonly

  • appendfsync

  • repl-timeout

Redis OSS 2.8.21 added parameters

Parameter group family: redis2.8

For Redis OSS 2.8.21, there are no additional parameters supported.

Redis OSS 2.8.19 added parameters

Parameter group family: redis2.8

For Redis OSS 2.8.19 there are no additional parameters supported.

Redis OSS 2.8.6 added parameters

Parameter group family: redis2.8

For Redis OSS 2.8.6 the following additional parameters are supported.

Name Details Description
min-slaves-max-lag

Default: 10

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

The number of seconds within which the primary node must receive a ping request from a read replica. If this amount of time passes and the primary does not receive a ping, then the replica is no longer considered available. If the number of available replicas drops below min-slaves-to-write, then the primary will stop accepting writes at that point.

If either this parameter or min-slaves-to-write is 0, then the primary node will always accept writes requests, even if no replicas are available.
min-slaves-to-write

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

The minimum number of read replicas which must be available in order for the primary node to accept writes from clients. If the number of available replicas falls below this number, then the primary node will no longer accept write requests.

If either this parameter or min-slaves-max-lag is 0, then the primary node will always accept writes requests, even if no replicas are available.
notify-keyspace-events

Default: (an empty string)

Type: string

Modifiable: Yes

Changes Take Effect: Immediately

The types of keyspace events that Redis OSS can notify clients of. Each event type is represented by a single letter:

  • K — Keyspace events, published with a prefix of __keyspace@<db>__

  • E — Key-event events, published with a prefix of __keyevent@<db>__

  • g — Generic, non-specific commands such as DEL, EXPIRE, RENAME, etc.

  • $ — String commands

  • l — List commands

  • s — Set commands

  • h — Hash commands

  • z — Sorted set commands

  • x — Expired events (events generated every time a key expires)

  • e — Evicted events (events generated when a key is evicted for maxmemory)

  • A — An alias for g$lshzxe

You can have any combination of these event types. For example, AKE means that Redis OSS can publish notifications of all event types.

Do not use any characters other than those listed above; attempts to do so will result in error messages.

By default, this parameter is set to an empty string, meaning that keyspace event notification is disabled.
repl-backlog-size

Default: 1048576

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

The size, in bytes, of the primary node backlog buffer. The backlog is used for recording updates to data at the primary node. When a read replica connects to the primary, it attempts to perform a partial sync (psync), where it applies data from the backlog to catch up with the primary node. If the psync fails, then a full sync is required.

The minimum value for this parameter is 16384.

Note

Beginning with Redis OSS 2.8.22, this parameter applies to the primary cluster as well as the read replicas.
repl-backlog-ttl

Default: 3600

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

The number of seconds that the primary node will retain the backlog buffer. Starting from the time the last replica node disconnected, the data in the backlog will remain intact until repl-backlog-ttl expires. If the replica has not connected to the primary within this time, then the primary will release the backlog buffer. When the replica eventually reconnects, it will have to perform a full sync with the primary.

If this parameter is set to 0, then the backlog buffer will never be released.
repl-timeout

Default: 60

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Represents the timeout period, in seconds, for:

  • Bulk data transfer during synchronization, from the read replica's perspective

  • Primary node timeout from the replica's perspective

  • Replica timeout from the primary node's perspective

Redis OSS 2.6.13 parameters

Parameter group family: redis2.6

Redis OSS 2.6.13 was the first version of Redis OSS supported by ElastiCache. The following table shows the Redis OSS 2.6.13 parameters that ElastiCache supports.

Name Details Description
activerehashing

Default: yes

Type: string (yes/no)

Modifiable: Yes

Changes take place: At Creation

Determines whether to enable Redis' active rehashing feature. The main hash table is rehashed ten times per second; each rehash operation consumes 1 millisecond of CPU time.

This value is set when you create the parameter group. When assigning a new parameter group to a cluster, this value must be the same in both the old and new parameter groups.
appendonly

Default: no

Type: string

Modifiable: Yes

Changes Take Effect: Immediately

Enables or disables Redis' append only file feature (AOF). AOF captures any Redis OSS commands that change data in the cache, and is used to recover from certain node failures.

The default value is no, meaning AOF is turned off. Set this parameter to yes to enable AOF.

For more information, see Mitigating Failures.

Note

Append Only Files (AOF) is not supported for cache.t1.micro and cache.t2.* nodes. For nodes of this type, the appendonly parameter value is ignored.

Note

For Multi-AZ replication groups, AOF is not allowed.
appendfsync

Default: everysec

Type: string

Modifiable: Yes

Changes Take Effect: Immediately

 When appendonly is set to yes, controls how often the AOF output buffer is written to disk:

  • no — the buffer is flushed to disk on an as-needed basis.

  • everysec — the buffer is flushed once per second. This is the default.

  • always — the buffer is flushed every time that data in the cluster is modified.

  • Appendfsync is not supported for versions 2.8.22 and later.

client-output-buffer-limit-normal-hard-limit

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

If a client's output buffer reaches the specified number of bytes, the client will be disconnected. The default is zero (no hard limit).
client-output-buffer-limit-normal-soft-limit

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 If a client's output buffer reaches the specified number of bytes, the client will be disconnected, but only if this condition persists for client-output-buffer-limit-normal-soft-seconds. The default is zero (no soft limit).
client-output-buffer-limit-normal-soft-seconds

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 If a client's output buffer remains at client-output-buffer-limit-normal-soft-limit bytes for longer than this number of seconds, the client will be disconnected. The default is zero (no time limit).
client-output-buffer-limit-pubsub-hard-limit

Default: 33554432

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

For Redis OSS publish/subscribe clients: If a client's output buffer reaches the specified number of bytes, the client will be disconnected.
client-output-buffer-limit-pubsub-soft-limit

Default: 8388608

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 For Redis OSS publish/subscribe clients: If a client's output buffer reaches the specified number of bytes, the client will be disconnected, but only if this condition persists for client-output-buffer-limit-pubsub-soft-seconds.
client-output-buffer-limit-pubsub-soft-seconds

Default: 60

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 For Redis OSS publish/subscribe clients: If a client's output buffer remains at client-output-buffer-limit-pubsub-soft-limit bytes for longer than this number of seconds, the client will be disconnected.
client-output-buffer-limit-slave-hard-limit

Default: For values see Redis OSS node-type specific parameters

Type: integer

Modifiable: No

 For Redis OSS read replicas: If a client's output buffer reaches the specified number of bytes, the client will be disconnected.
client-output-buffer-limit-slave-soft-limit

Default: For values see Redis OSS node-type specific parameters

Type: integer

Modifiable: No

 For Redis OSS read replicas: If a client's output buffer reaches the specified number of bytes, the client will be disconnected, but only if this condition persists for client-output-buffer-limit-slave-soft-seconds.
client-output-buffer-limit-slave-soft-seconds

Default: 60

Type: integer

Modifiable: No

 For Redis OSS read replicas: If a client's output buffer remains at client-output-buffer-limit-slave-soft-limit bytes for longer than this number of seconds, the client will be disconnected.
databases

Default: 16

Type: integer

Modifiable: No

Changes take place: At Creation

The number of logical partitions the databases is split into. We recommend keeping this value low.

This value is set when you create the parameter group. When assigning a new parameter group to a cluster, this value must be the same in both the old and new parameter groups.
hash-max-ziplist-entries

Default: 512

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Determines the amount of memory used for hashes. Hashes with fewer than the specified number of entries are stored using a special encoding that saves space.
hash-max-ziplist-value

Default: 64

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Determines the amount of memory used for hashes. Hashes with entries that are smaller than the specified number of bytes are stored using a special encoding that saves space.
list-max-ziplist-entries

Default: 512

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Determines the amount of memory used for lists. Lists with fewer than the specified number of entries are stored using a special encoding that saves space.
list-max-ziplist-value

Default: 64

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Determines the amount of memory used for lists. Lists with entries that are smaller than the specified number of bytes are stored using a special encoding that saves space.
lua-time-limit

Default: 5000

Type: integer

Modifiable: No

 The maximum execution time for a Lua script, in milliseconds, before ElastiCache takes action to stop the script.

If lua-time-limit is exceeded, all Redis OSS commands will return an error of the form ____-BUSY. Since this state can cause interference with many essential Redis OSS operations, ElastiCache will first issue a SCRIPT KILL command. If this is unsuccessful, ElastiCache will forcibly restart Redis OSS.
maxclients This value applies to all instance types except those explicity specified

Default: 65000

Type: integer

Modifiable: No

 The maximum number of clients that can be connected at one time.

t2.medium Default: 20000

Type: integer

Modifiable: No

t2.small Default: 20000

Type: integer

Modifiable: No

t2.micro Default: 20000

Type: integer

Modifiable: No

t4g.micro Default: 20000

Type: integer

Modifiable: No

t3.medium Default: 46000

Type: integer

Modifiable: No

t3.small Default: 46000

Type: integer

Modifiable: No

t3.micro Default: 20000

Type: integer

Modifiable: No
maxmemory-policy

Default: volatile-lru

Type: string

Modifiable: Yes

Changes Take Effect: Immediately

 The eviction policy for keys when maximum memory usage is reached.

Valid values are: volatile-lru | allkeys-lru | volatile-random | allkeys-random | volatile-ttl | noeviction

For more information, see Using Valkey or Redis OSS as an LRU cache.
maxmemory-samples

Default: 3

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 For least-recently-used (LRU) and time-to-live (TTL) calculations, this parameter represents the sample size of keys to check. By default, Redis OSS chooses 3 keys and uses the one that was used least recently.
reserved-memory

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

The total memory, in bytes, reserved for non-data usage. By default, the Redis OSS node will grow until it consumes the node's maxmemory (see Redis OSS node-type specific parameters). If this occurs, then node performance will likely suffer due to excessive memory paging. By reserving memory you can set aside some of the available memory for non-Redis OSS purposes to help reduce the amount of paging.

This parameter is specific to ElastiCache, and is not part of the standard Redis OSS distribution.

For more information, see reserved-memory-percent and Managing reserved memory for Valkey and Redis OSS.
set-max-intset-entries

Default: 512

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Determines the amount of memory used for certain kinds of sets (strings that are integers in radix 10 in the range of 64 bit signed integers). Such sets with fewer than the specified number of entries are stored using a special encoding that saves space.
slave-allow-chaining

Default: no

Type: string

Modifiable: No

 Determines whether a read replica in Redis OSS can have read replicas of its own.
slowlog-log-slower-than

Default: 10000

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 The maximum execution time, in microseconds, for commands to be logged by the Redis OSS Slow Log feature.
slowlog-max-len

Default: 128

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 The maximum length of the Redis OSS Slow Log.
tcp-keepalive

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 If this is set to a nonzero value (N), node clients are polled every N seconds to ensure that they are still connected. With the default setting of 0, no such polling occurs.
Important

Some aspects of this parameter changed in Redis OSS version 3.2.4. See Parameters changed in Redis OSS 3.2.4 (enhanced).
timeout

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 The number of seconds a node waits before timing out. Values are:

  • 0 – never disconnect an idle client.

  • 1-19 – invalid values.

  • >=20 – the number of seconds a node waits before disconnecting an idle client.
zset-max-ziplist-entries

Default: 128

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Determines the amount of memory used for sorted sets. Sorted sets with fewer than the specified number of elements are stored using a special encoding that saves space.
zset-max-ziplist-value

Default: 64

Type: integer

Modifiable: Yes

Changes Take Effect: Immediately

 Determines the amount of memory used for sorted sets. Sorted sets with entries that are smaller than the specified number of bytes are stored using a special encoding that saves space.
Note

If you do not specify a parameter group for your Redis OSS 2.6.13 cluster, then a default parameter group (default.redis2.6) will be used. You cannot change the values of any parameters in the default parameter group; however, you can always create a custom parameter group and assign it to your cluster at any time.

Redis OSS node-type specific parameters

Although most parameters have a single value, some parameters have different values depending on the node type used. The following table shows the default values for the maxmemory, client-output-buffer-limit-slave-hard-limit, and client-output-buffer-limit-slave-soft-limit parameters for each node type. The value of maxmemory is the maximum number of bytes available to you for use, data and other uses, on the node. For more information, see Available memory.

Note

The maxmemory parameter cannot be modified.

Node type Maxmemory Client-output-buffer-limit-slave-hard-limit Client-output-buffer-limit-slave-soft-limit
cache.t1.micro 142606336 14260633 14260633
cache.t2.micro 581959680 58195968 58195968
cache.t2.small 1665138688 166513868 166513868
cache.t2.medium 3461349376 346134937 346134937
cache.t3.micro 536870912 53687091 53687091
cache.t3.small 1471026299 147102629 147102629
cache.t3.medium 3317862236 331786223 331786223
cache.t4g.micro 536870912 53687091 53687091
cache.t4g.small 1471026299 147102629 147102629
cache.t4g.medium 3317862236 331786223 331786223
cache.m1.small 943718400 94371840 94371840
cache.m1.medium 3093299200 309329920 309329920
cache.m1.large 7025459200 702545920 702545920
cache.m1.xlarge 14889779200 1488977920 1488977920
cache.m2.xlarge 17091788800 1709178880 1709178880
cache.m2.2xlarge 35022438400 3502243840 3502243840
cache.m2.4xlarge 70883737600 7088373760 7088373760
cache.m3.medium 2988441600 309329920 309329920
cache.m3.large 6501171200 650117120 650117120
cache.m3.xlarge 14260633600 1426063360 1426063360
cache.m3.2xlarge 29989273600 2998927360 2998927360
cache.m4.large 6892593152 689259315 689259315
cache.m4.xlarge 15328501760 1532850176 1532850176
cache.m4.2xlarge 31889126359 3188912636 3188912636
cache.m4.4xlarge 65257290629 6525729063 6525729063
cache.m4.10xlarge 166047614239 16604761424 16604761424
cache.m5.large 6854542746 685454275 685454275
cache.m5.xlarge 13891921715 1389192172 1389192172
cache.m5.2xlarge 27966669210 2796666921 2796666921
cache.m5.4xlarge 56116178125 5611617812 5611617812
cache.m5.12xlarge 168715971994 16871597199 16871597199
cache.m5.24xlarge 337500562842 33750056284 33750056284
cache.m6g.large 6854542746 685454275 685454275
cache.m6g.xlarge 13891921715 1389192172 1389192172
cache.m6g.2xlarge 27966669210 2796666921 2796666921
cache.m6g.4xlarge 56116178125 5611617812 5611617812
cache.m6g.8xlarge 111325552312 11132555231 11132555231
cache.m6g.12xlarge 168715971994 16871597199 16871597199
cache.m6g.16xlarge 225000375228 22500037523 22500037523
cache.c1.xlarge 6501171200 650117120 650117120
cache.r3.large 14470348800 1468006400 1468006400
cache.r3.xlarge 30513561600 3040870400 3040870400
cache.r3.2xlarge 62495129600 6081740800 6081740800
cache.r3.4xlarge 126458265600 12268339200 12268339200
cache.r3.8xlarge 254384537600 24536678400 24536678400
cache.r4.large 13201781556 1320178155 1320178155
cache.r4.xlarge 26898228839 2689822883 2689822883
cache.r4.2xlarge 54197537997 5419753799 5419753799
cache.r4.4xlarge 108858546586 10885854658 10885854658
cache.r4.8xlarge 218255432090 21825543209 21825543209
cache.r4.16xlarge 437021573120 43702157312 43702157312
cache.r5.large 14037181030 1403718103 1403718103
cache.r5.xlarge 28261849702 2826184970 2826184970
cache.r5.2xlarge 56711183565 5671118356 5671118356
cache.r5.4xlarge 113609865216 11360986522 11360986522
cache.r5.12xlarge 341206346547 34120634655 34120634655
cache.r5.24xlarge 682485973811 68248597381 68248597381
cache.r6g.large 14037181030 1403718103 1403718103
cache.r6g.xlarge 28261849702 2826184970 2826184970
cache.r6g.2xlarge 56711183565 5671118356 5671118356
cache.r6g.4xlarge 113609865216 11360986522 11360986522
cache.r6g.8xlarge 225000375228 22500037523 22500037523
cache.r6g.12xlarge 341206346547 34120634655 34120634655
cache.r6g.16xlarge 450000750456 45000075046 45000075046
cache.r6gd.xlarge 28261849702 2826184970 2826184970
cache.r6gd.2xlarge 56711183565 5671118356 5671118356
cache.r6gd.4xlarge 113609865216 11360986522 11360986522
cache.r6gd.8xlarge 225000375228 22500037523 22500037523
cache.r6gd.12xlarge 341206346547 34120634655 34120634655
cache.r6gd.16xlarge 450000750456 45000075046 45000075046
cache.r7g.large 14037181030 1403718103 1403718103
cache.r7g.xlarge 28261849702 2826184970 2826184970
cache.r7g.2xlarge 56711183565 5671118356 5671118356
cache.r7g.4xlarge 113609865216 11360986522 11360986522
cache.r7g.8xlarge 225000375228 22500037523 22500037523
cache.r7g.12xlarge 341206346547 34120634655 34120634655
cache.r7g.16xlarge 450000750456 45000075046 45000075046
cache.m7g.large 6854542746 685454275 685454275
cache.m7g.xlarge 13891921715 1389192172 1389192172
cache.m7g.2xlarge 27966669210 2796666921 2796666921
cache.m7g.4xlarge 56116178125 5611617812 5611617812
cache.m7g.8xlarge 111325552312 11132555231 11132555231
cache.m7g.12xlarge 168715971994 16871597199 16871597199
cache.m7g.16xlarge 225000375228 22500037523 22500037523
cache.c7gn.large 3317862236 1403718103 1403718103
cache.c7gn.xlarge 6854542746 2826184970 2826184970
cache.c7gn.2xlarge 13891921715 5671118356 5671118356
cache.c7gn.4xlarge 27966669210 11360986522 11360986522
cache.c7gn.8xlarge 56116178125 22500037523 22500037523
cache.c7gn.12xlarge 84357985997 34120634655 34120634655
cache.c7gn.16xlarge 113609865216 45000075046 45000075046
Note

All current generation instance types are created in an Amazon Virtual Private Cloud VPC by default.

T1 instances do not support Multi-AZ.

T1 and T2 instances do not support Redis OSS AOF.

Redis OSS configuration variables appendonly and appendfsync are not supported on Redis OSS version 2.8.22 and later.

Memcached specific parameters

Memcached

If you do not specify a parameter group for your Memcached cluster, then a default parameter group appropriate to your engine version will be used. You can't change the values of any parameters in a default parameter group. However, you can create a custom parameter group and assign it to your cluster at any time. For more information, see Creating an ElastiCache parameter group.

Memcached 1.6.17 changes

From Memcached 1.6.17, we no longer support these administrative commands: lru_crawler, lru, and slabs. With these changes, you will not be able to enable/disable lru_crawler at runtime via commands. Please enable/disable lru_crawler by modifying your custom parameter group.

Memcached 1.6.6 added parameters

For Memcached 1.6.6, no additional parameters are supported.

Parameter group family: memcached1.6

Memcached 1.5.10 parameter changes

For Memcached 1.5.10, the following additional parameters are supported.

Parameter group family: memcached1.5

Name Details Description
no_modern

Default: 1

Type: boolean

Modifiable: Yes

Allowed_Values: 0,1

Changes Take Effect: At launch

An alias for disabling slab_reassign, lru_maintainer_thread, lru_segmented, andmaxconns_fast commands.

When using Memcached 1.5 and higher, no_modern also sets the hash_algorithm to jenkins.

In addition, when using Memcached 1.5.10, inline_ascii_reponse is controlled by the parameter parallelly. This means that if no_modern is disabled then inline_ascii_reponse is disabled. From Memcached engine 1.5.16 onward the inline_ascii_response parameter no longer applies, so no_modern being abled or disabled has no effect on inline_ascii_reponse.

If no_modern is disabled, then slab_reassign, lru_maintainer_thread, lru_segmented, and maxconns_fast WILL be enabled. Since slab_automove and hash_algorithm parameters are not SWITCH parameters, their setting is based on the configurations in the parameter group.

If you want to disable no_modern and revert to modern, you must configure a custom parameter group to disable this parameter and then reboot for these changes to take effect.

Note

The default configuration value for this parameter has been changed from 0 to 1 as of August 20, 2021. The updated default value will get automatically picked up by new ElastiCache users for each regions after August 20th, 2021. Existing ElastiCache users in the regions before August 20th, 2021 need to manually modify their custom parameter groups in order to pick up this new change.
inline_ascii_resp

Default: 0

Type: boolean

Modifiable: Yes

Allowed_Values: 0,1

Changes Take Effect: At launch

Stores numbers from VALUE response, inside an item, using up to 24 bytes. Small slowdown for ASCII get, faster sets.

For Memcached 1.5.10, the following parameters are removed.

Name Details Description
expirezero_does_not_evict

Default: 0

Type: boolean

Modifiable: Yes

Allowed_Values: 0,1

Changes Take Effect: At launch

No longer supported in this version.
modern

Default: 1

Type: boolean

Modifiable: Yes (requires re-launch if set to no_modern)

Allowed_Values: 0,1

Changes Take Effect: At launch

No longer supported in this version. Starting with this version, no-modern is enabled by default with every launch or re-launch.

Memcached 1.4.34 added parameters

For Memcached 1.4.34, no additional parameters are supported.

Parameter group family: memcached1.4

Memcached 1.4.33 added parameters

For Memcached 1.4.33, the following additional parameters are supported.

Parameter group family: memcached1.4

Name Details Description
modern

Default: enabled

Type: boolean

Modifiable: Yes

Changes Take Effect: At launch

An alias to multiple features. Enabling modern is equivalent to turning following commands on and using a murmur3 hash algorithm: slab_reassign, slab_automove, lru_crawler, lru_maintainer, maxconns_fast, and hash_algorithm=murmur3.
watch

Default: enabled

Type: boolean

Modifiable: Yes

Changes Take Effect: Immediately

Logs can get dropped if user hits their watcher_logbuf_size and worker_logbuf_size limits.

Logs fetches, evictions or mutations. When, for example, user turns watch on, they can see logs when get, set, delete, or update occur.
idle_timeout

Default: 0 (disabled)

Type: integer

Modifiable: Yes

Changes Take Effect: At Launch

The minimum number of seconds a client will be allowed to idle before being asked to close. Range of values: 0 to 86400.
track_sizes

Default: disabled

Type: boolean

Modifiable: Yes

Changes Take Effect: At Launch

Shows the sizes each slab group has consumed.

Enabling track_sizes lets you run stats sizes without the need to run stats sizes_enable.
watcher_logbuf_size

Default: 256 (KB)

Type: integer

Modifiable: Yes

Changes Take Effect: At Launch

The watch command turns on stream logging for Memcached. However watch can drop logs if the rate of evictions, mutations or fetches are high enough to cause the logging buffer to become full. In such situations, users can increase the buffer size to reduce the chance of log losses.
worker_logbuf_size

Default: 64 (KB)

Type: integer

Modifiable: Yes

Changes Take Effect: At Launch

The watch command turns on stream logging for Memcached. However watch can drop logs if the rate of evictions, mutations or fetches are high enough to cause logging buffer get full. In such situations, users can increase the buffer size to reduce the chance of log losses.
slab_chunk_max

Default: 524288 (bytes)

Type: integer

Modifiable: Yes

Changes Take Effect: At Launch

Specifies the maximum size of a slab. Setting smaller slab size uses memory more efficiently. Items larger than slab_chunk_max are split over multiple slabs.
lru_crawler metadump [all|1|2|3]

Default: disabled

Type: boolean

Modifiable: Yes

Changes Take Effect: Immediately

if lru_crawler is enabled this command dumps all keys.

all|1|2|3 - all slabs, or specify a particular slab number

Memcached 1.4.24 added parameters

For Memcached 1.4.24, the following additional parameters are supported.

Parameter group family: memcached1.4

Name Details Description
disable_flush_all

Default: 0 (disabled)

Type: boolean

Modifiable: Yes

Changes Take Effect: At launch

Add parameter (-F) to disable flush_all. Useful if you never want to be able to run a full flush on production instances.

Values: 0, 1 (user can do a flush_all when the value is 0).
hash_algorithm

Default: jenkins

Type: string

Modifiable: Yes

Changes Take Effect: At launch

 The hash algorithm to be used. Permitted values: murmur3 and jenkins.
lru_crawler

Default: 0 (disabled)

Type: boolean

Modifiable: Yes

Changes Take Effect: After restart

Note

You can temporarily enable lru_crawler at runtime from the command line. For more information, see the Description column.

Cleans slab classes of items that have expired. This is a low impact process that runs in the background. Currently requires initiating a crawl using a manual command.

To temporarily enable, run lru_crawler enable at the command line.

lru_crawler 1,3,5 crawls slab classes 1, 3, and 5 looking for expired items to add to the freelist.

Values: 0,1

Note

Enabling lru_crawler at the command line enables the crawler until either disabled at the command line or the next reboot. To enable permanently, you must modify the parameter value. For more information, see Modifying an ElastiCache parameter group.
lru_maintainer

Default: 0 (disabled)

Type: boolean

Modifiable: Yes

Changes Take Effect: At launch

A background thread that shuffles items between the LRUs as capacities are reached. Values: 0, 1.

expirezero_does_not_evict

Default: 0 (disabled)

Type: boolean

Modifiable: Yes

Changes Take Effect: At launch

When used with lru_maintainer, makes items with an expiration time of 0 unevictable.

Warning

This can crowd out memory available for other evictable items.

Can be set to disregard lru_maintainer.

Memcached 1.4.14 added parameters

For Memcached 1.4.14, the following additional parameters are supported.

Parameter group family: memcached1.4

Parameters added in Memcached 1.4.14
Name Details Description
config_max

Default: 16

Type: integer

Modifiable: No

 The maximum number of ElastiCache configuration entries.
config_size_max

Default: 65536

Type: integer

Modifiable: No

 The maximum size of the configuration entries, in bytes.
hashpower_init

Default: 16

Type: integer

Modifiable: No

 The initial size of the ElastiCache hash table, expressed as a power of two. The default is 16 (2^16), or 65536 keys.
maxconns_fast

Default: 0 (false)

Type: Boolean

Modifiable: Yes

Changes Take Effect: After restart

 Changes the way in which new connections requests are handled when the maximum connection limit is reached. If this parameter is set to 0 (zero), new connections are added to the backlog queue and will wait until other connections are closed. If the parameter is set to 1, ElastiCache sends an error to the client and immediately closes the connection.
slab_automove

Default: 0

Type: integer

Modifiable: Yes

Changes Take Effect: After restart

 Adjusts the slab automove algorithm: If this parameter is set to 0 (zero), the automove algorithm is disabled. If it is set to 1, ElastiCache takes a slow, conservative approach to automatically moving slabs. If it is set to 2, ElastiCache aggressively moves slabs whenever there is an eviction. (This mode is not recommended except for testing purposes.)
slab_reassign

Default: 0 (false)

Type: Boolean

Modifiable: Yes

Changes Take Effect: After restart

 Enable or disable slab reassignment. If this parameter is set to 1, you can use the "slabs reassign" command to manually reassign memory.

Memcached 1.4.5 supported parameters

Parameter group family: memcached1.4

For Memcached 1.4.5, the following parameters are supported.

Parameters added in Memcached 1.4.5
Name Details Description
backlog_queue_limit

Default: 1024

Type: integer

Modifiable: No

 The backlog queue limit.
binding_protocol

Default: auto

Type: string

Modifiable: Yes

Changes Take Effect: After restart

 The binding protocol.

Permissible values are: ascii and auto.

For guidance on modifying the value of binding_protocol, see Modifying an ElastiCache parameter group.
cas_disabled

Default: 0 (false)

Type: Boolean

Modifiable: Yes

Changes Take Effect: After restart

 If 1 (true), check and set (CAS) operations will be disabled, and items stored will consume 8 fewer bytes than with CAS enabled.
chunk_size

Default: 48

Type: integer

Modifiable: Yes

Changes Take Effect: After restart

 The minimum amount, in bytes, of space to allocate for the smallest item's key, value, and flags.
chunk_size_growth_factor

Default: 1.25

Type: float

Modifiable: Yes

Changes Take Effect: After restart

 The growth factor that controls the size of each successive Memcached chunk; each chunk will be chunk_size_growth_factor times larger than the previous chunk.
error_on_memory_exhausted

Default: 0 (false)

Type: Boolean

Modifiable: Yes

Changes Take Effect: After restart

 If 1 (true), when there is no more memory to store items, Memcached will return an error rather than evicting items.
large_memory_pages

Default: 0 (false)

Type: Boolean

Modifiable: No

 If 1 (true), ElastiCache will try to use large memory pages.
lock_down_paged_memory

Default: 0 (false)

Type: Boolean

Modifiable: No

 If 1 (true), ElastiCache will lock down all paged memory.
max_item_size

Default: 1048576

Type: integer

Modifiable: Yes

Changes Take Effect: After restart

 The size, in bytes, of the largest item that can be stored in the cluster.
max_simultaneous_connections

Default: 65000

Type: integer

Modifiable: No

 The maximum number of simultaneous connections.
maximize_core_file_limit

Default: 0 (false)

Type: Boolean

Modifiable:

Changes Take Effect: After restart

 If 1 (true), ElastiCache will maximize the core file limit.
memcached_connections_overhead

Default: 100

Type: integer

Modifiable: Yes

Changes Take Effect: After restart

 The amount of memory to be reserved for Memcached connections and other miscellaneous overhead. For information about this parameter, see Memcached connection overhead.
requests_per_event

Default: 20

Type: integer

Modifiable: No

 The maximum number of requests per event for a given connection. This limit is required to prevent resource starvation.

Memcached connection overhead

On each node, the memory made available for storing items is the total available memory on that node (which is stored in the max_cache_memory parameter) minus the memory used for connections and other overhead (which is stored in the memcached_connections_overhead parameter). For example, a node of type cache.m1.small has a max_cache_memory of 1300MB. With the default memcached_connections_overhead value of 100MB, the Memcached process will have 1200MB available to store items.

The default values for the memcached_connections_overhead parameter satisfy most use cases; however, the required amount of allocation for connection overhead can vary depending on multiple factors, including request rate, payload size, and the number of connections.

You can change the value of the memcached_connections_overhead to better suit the needs of your application. For example, increasing the value of the memcached_connections_overhead parameter will reduce the amount of memory available for storing items and provide a larger buffer for connection overhead. Decreasing the value of the memcached_connections_overhead parameter will give you more memory to store items, but can increase your risk of swap usage and degraded performance. If you observe swap usage and degraded performance, try increasing the value of the memcached_connections_overhead parameter.

Important

For the cache.t1.micro node type, the value for memcached_connections_overhead is determined as follows:

  • If you cluster is using the default parameter group, ElastiCache will set the value for memcached_connections_overhead to 13MB.

  • If your cluster is using a parameter group that you have created yourself, you can set the value of memcached_connections_overhead to a value of your choice.

Memcached node-type specific parameters

Although most parameters have a single value, some parameters have different values depending on the node type used. The following table shows the default values for the max_cache_memory and num_threads parameters for each node type. The values on these parameters cannot be modified.

Node type max_cache_memory (in megabytes) num_threads
cache.t1.micro 213 1
cache.t2.micro 555 1
cache.t2.small 1588 1
cache.t2.medium 3301 2
cache.t3.micro 512 2
cache.t3.small 1402 2
cache.t3.medium 3364 2
cache.t4g.micro 512 2
cache.t4g.small 1402 2
cache.t4g.medium 3164 2
cache.m1.small 1301 1
cache.m1.medium 3350 1
cache.m1.large 7100 2
cache.m1.xlarge 14600 4
cache.m2.xlarge 33800 2
cache.m2.2xlarge 30412 4
cache.m2.4xlarge 68000 16
cache.m3.medium 2850 1
cache.m3.large 6200 2
cache.m3.xlarge 13600 4
cache.m3.2xlarge 28600 8
cache.m4.large 6573 2
cache.m4.xlarge 11496 4
cache.m4.2xlarge 30412 8
cache.m4.4xlarge 62234 16
cache.m4.10xlarge 158355 40
cache.m5.large 6537 2
cache.m5.xlarge 13248 4
cache.m5.2xlarge 26671 8
cache.m5.4xlarge 53516 16
cache.m5.12xlarge 160900 48
cache.m5.24xlarge 321865 96
cache.m6g.large 6537 2
cache.m6g.xlarge 13248 4
cache.m6g.2xlarge 26671 8
cache.m6g.4xlarge 53516 16
cache.m6g.8xlarge 107000 32
cache.m6g.12xlarge 160900 48
cache.m6g.16xlarge 214577 64
cache.c1.xlarge 6600 8
cache.r3.large 13800 2
cache.r3.xlarge 29100 4
cache.r3.2xlarge 59600 8
cache.r3.4xlarge 120600 16
cache.r3.8xlarge 120600 32
cache.r4.large 12590 2
cache.r4.xlarge 25652 4
cache.r4.2xlarge 51686 8
cache.r4.4xlarge 103815 16
cache.r4.8xlarge 208144 32
cache.r4.16xlarge 416776 64
cache.r5.large 13387 2
cache.r5.xlarge 26953 4
cache.r5.2xlarge 54084 8
cache.r5.4xlarge 108347 16
cache.r5.12xlarge 325400 48
cache.r5.24xlarge 650869 96
cache.r6g.large 13387 2
cache.r6g.xlarge 26953 4
cache.r6g.2xlarge 54084 8
cache.r6g.4xlarge 108347 16
cache.r6g.8xlarge 214577 32
cache.r6g.12xlarge 325400 48
cache.r6g.16xlarge 429154 64
cache.c7gn.large 3164 2
cache.c7gn.xlarge 6537 4
cache.c7gn.2xlarge 13248 8
cache.c7gn.4xlarge 26671 16
cache.c7gn.8xlarge 53516 32
cache.c7gn.12xlarge 325400 48
cache.c7gn.16xlarge 108347 64
Note

All T2 instances are created in an Amazon Virtual Private Cloud (Amazon VPC).