Amazon RDS DB instance storage

DB instances for Amazon RDS for MySQL, MariaDB, PostgreSQL, Oracle, and Microsoft SQL Server use Amazon Elastic Block Store (Amazon EBS) volumes for database and log storage.

In some cases, your database workload might not be able to achieve 100 percent of the IOPS that you have provisioned. For more information, see Factors that affect storage performance.

For more information about instance storage pricing, see Amazon RDS pricing.

Amazon RDS storage types

Amazon RDS provides three storage types: General Purpose SSD (also known as gp2 and gp3), Provisioned IOPS SSD (also known as io1), and magnetic (also known as standard). They differ in performance characteristics and price, which means that you can tailor your storage performance and cost to the needs of your database workload. You can create MySQL, MariaDB, Oracle, and PostgreSQL RDS DB instances with up to 64 tebibytes (TiB) of storage. You can create SQL Server RDS DB instances with up to 16 TiB of storage. For this amount of storage, use the Provisioned IOPS SSD and General Purpose SSD storage types.

The following list briefly describes the three storage types:

• General Purpose SSD – General Purpose SSD volumes offer cost-effective storage that is ideal for a broad range of workloads running on medium-sized DB instances. General Purpose storage is best suited for development and testing environments.

  For more information about General Purpose SSD storage, including the storage size ranges, see General Purpose SSD storage.

• Provisioned IOPS SSD – Provisioned IOPS storage is designed to meet the needs of I/O-intensive workloads, particularly database workloads, that require low I/O latency and consistent I/O throughput. Provisioned IOPS storage is best suited for production environments.

  For more information about Provisioned IOPS storage, including the storage size ranges, see Provisioned IOPS SSD storage.

• Magnetic – Amazon RDS also supports magnetic storage for backward compatibility. We recommend that you use General Purpose SSD or Provisioned IOPS SSD for any new storage needs. The maximum amount of storage allowed for DB instances on magnetic storage is less than that of the other storage types. For more information, see Magnetic storage.

When you select General Purpose SSD or Provisioned IOPS SSD, depending on the engine selected and the amount of storage requested, Amazon RDS automatically stripes across multiple volumes to enhance performance, as shown in the following table.

Database engine	Amazon RDS storage size	Amount of volumes provisioned
MariaDB, MySQL, and PostgreSQL	Less than 400 GiB	1
MariaDB, MySQL, and PostgreSQL	Between 400 and 64,000 GiB	4
Oracle	Less than 200 GiB	1
Oracle	Between 200 and 64,000 GiB	4
SQL Server	Any	1

When you modify a General Purpose SSD or Provisioned IOPS SSD volume, it goes through a sequence of states. While the volume is in the optimizing state, your volume performance is in between the source and target configuration specifications. Transitional volume performance will be no less than the lowest of the two specifications. For more information on volume modifications, see Monitor the progress of volume modifications in the Amazon EC2 User Guide.

Important

When you modify an instance’s storage so that it goes from one volume to four volumes, or when you modify an instance using magnetic storage, Amazon RDS does not use the Elastic Volumes feature. Instead, Amazon RDS provisions new volumes and transparently moves the data from the old volume to the new volumes. This operation consumes a significant amount of IOPS and throughput of both the old and new volumes. Depending on the size of the volume and the amount of database workload present during the modification, this operation can consume a high amount of IOPS, significantly increase IO latency, and take several hours to complete, while the RDS instance remains in the Modifying state.

General Purpose SSD storage

General Purpose SSD storage offers cost-effective storage that is acceptable for most database workloads that aren't latency sensitive.

Note

DB instances that use General Purpose SSD storage can experience much longer latency after read replica creation, Multi-AZ conversion, and DB snapshot restoration than instances that use Provisioned IOPS storage. If you need a DB instance with minimum latency after these operations, we recommend using Provisioned IOPS SSD storage.

Amazon RDS offers two types of General Purpose SSD storage: gp2 storage and gp3 storage.

gp2 storage

When your applications don't need high storage performance, you can use General Purpose SSD gp2 storage. Baseline I/O performance for gp2 storage is 3 IOPS for each GiB, with a minimum of 100 IOPS. This relationship means that larger volumes have better performance. For example, baseline performance for one 100-GiB volume is 300 IOPS. Baseline performance for one 1,000 GiB volume is 3,000 IOPS. Maximum baseline performance for one gp2 volume (5334 GiB and greater) is 16,000 IOPS.

Individual gp2 volumes below 1,000 GiB in size also have the ability to burst to 3,000 IOPS for extended periods of time. Volume I/O credit balance determines burst performance. For more information about volume I/O credits, see I/O credits and burst performance in the Amazon EC2 User Guide. For a more detailed description of how baseline performance and I/O credit balance affect performance, see the post Understanding burst vs. baseline performance with Amazon RDS and gp2 on the AWS Database Blog.

Many workloads never deplete the burst balance. However, some workloads can exhaust the 3,000 IOPS burst storage credit balance, so you should plan your storage capacity to meet the needs of your workloads.

For gp2 volumes larger than 1,000 GiB, the baseline performance is greater than the burst performance. For such volumes, burst is irrelevant because the baseline performance is better than the 3,000 IOPS burst performance. However, for DB instances of certain engines and sizes, storage is striped across four volumes providing four times the baseline throughput, and four times the burst IOPS of a single volume. Storage performance for gp2 volumes on Amazon RDS DB engines, including the threshold, is shown in the following table.

DB engine	RDS Storage size	Range of Baseline IOPS	Range of Baseline Throughput	Burst IOPS
MariaDB, MySQL, and PostgreSQL	Between 20 and 399 GiB	100-1197 IOPS	128-250 MiB/s	3,000
MariaDB, MySQL, and PostgreSQL	Between 400 and 1,335 GiB	1,200-4,005 IOPS	500-1,000 MiB/s	12,000
MariaDB, MySQL, and PostgreSQL	Between 1,336 and 3,999 GiB	4008-11,997 IOPS	1,000 MiB/s	12,000
MariaDB, MySQL, and PostgreSQL	Between 4,000 and 65,536 GiB	12,000-64,000 IOPS	1,000 MiB/s	N/A*
Oracle	Between 20 and 199 GiB	100-597 IOPS	128-250 MiB/s	3,000
Oracle	Between 200 and 1,335 GiB	600-4,005 IOPS	500-1,000 MiB/s	12,000
Oracle	Between 1,336 and 3,999 GiB	4008-11,997 IOPS	1,000 MiB/s	12,000
Oracle	Between 4,000 and 65,536 GiB	12,000-64,000 IOPS	1,000 MiB/s	N/A*
SQL Server	Between 20 and 333 GiB	100-999 IOPS	128-250 MiB/s	3,000
SQL Server	Between 334 and 999 GiB	1,002-2,997 IOPS	250 MiB/s	3,000
SQL Server	Between 1,000 and 16,384 GiB	3,000-16,000 IOPS	250 MiB/s	N/A*

* The baseline performance of the volume exceeds the maximum burst performance.

gp3 storage

By using General Purpose SSD gp3 storage volumes, you can customize storage performance independently of storage capacity. Storage performance is the combination of I/O operations per second (IOPS) and how fast the storage volume can perform reads and writes (storage throughput). On gp3 storage volumes, Amazon RDS provides a baseline storage performance of 3000 IOPS and 125 MiB/s.

For every RDS DB engine except RDS for SQL Server, when the storage size for gp3 volumes reaches a certain threshold, the baseline storage performance increases to 12,000 IOPS and 500 MiB/s. This is because of volume striping, where the storage uses four volumes instead of one. RDS for SQL Server doesn't support volume striping, and therefore doesn't have a threshold value.

Note

General Purpose SSD gp3 storage is supported on Single-AZ and Multi-AZ DB instances, but isn't supported on Multi-AZ DB clusters. For more information, see Configuring and managing a Multi-AZ deployment and Multi-AZ DB cluster deployments.

Storage performance for gp3 volumes on Amazon RDS DB engines, including the threshold, is shown in the following table.

DB engine	Storage size	Baseline storage performance	Range of Provisioned IOPS	Range of provisioned storage throughput
MariaDB, MySQL, and PostgreSQL	Less than 400 GiB	3,000 IOPS/125 MiB/s	N/A	N/A
MariaDB, MySQL, and PostgreSQL	400 GiB and higher	12,000 IOPS/500 MiB/s	12,000–64,000 IOPS	500–4,000 MiB/s
Oracle	Less than 200 GiB	3,000 IOPS/125 MiB/s	N/A	N/A
Oracle	200 GiB and higher	12,000 IOPS/500 MiB/s	12,000–64,000 IOPS	500–4,000 MiB/s
SQL Server	20 GiB–16 TiB	3,000 IOPS/125 MiB/s	3,000–16,000 IOPS	125–1,000 MiB/s

For every DB engine except RDS for SQL Server, you can provision additional IOPS and storage throughput when storage size is at or above the threshold value. For RDS for SQL Server, you can provision additional IOPS and storage throughput for any available storage size. For all DB engines, you pay for only the additional provisioned storage performance. For more information, see Amazon RDS pricing.

Although the added Provisioned IOPS and storage throughput aren't dependent on the storage size, they are related to each other. When you raise the IOPS above 32,000 for MariaDB and MySQL, the storage throughput value automatically increases from 500 MiB/s. For example, when you set the IOPS to 40,000 on RDS for MySQL, the storage throughput must be at least 625 MiB/s. The automatic increase doesn't happen for Oracle, PostgreSQL, and SQL Server DB instances.

Storage performance values for gp3 volumes on RDS have the following constraints:

• The maximum ratio of storage throughput to IOPS is 0.25 for all supported DB engines.

• The minimum ratio of IOPS to allocated storage (in GiB) is 0.5 on RDS for SQL Server. There is no minimum ratio for the other supported DB engines.

• The maximum ratio of IOPS to allocated storage is 500 for all supported DB engines.

• If you're using storage autoscaling, the same ratios between IOPS and maximum storage threshold (in GiB) also apply.

  For more information on storage autoscaling, see Managing capacity automatically with Amazon RDS storage autoscaling.

Provisioned IOPS SSD storage

For a production application that requires fast and consistent I/O performance, we recommend Provisioned IOPS storage. Provisioned IOPS storage is a storage type that delivers predictable performance, and consistently low latency. Provisioned IOPS storage is optimized for online transaction processing (OLTP) workloads that require consistent performance. Provisioned IOPS helps performance tuning of these workloads.

When you create a DB instance, you specify the IOPS rate and the size of the volume. Amazon RDS provides that IOPS rate for the DB instance until you change it.

io1 storage

For I/O-intensive workloads, you can use Provisioned IOPS SSD io1 storage and achieve up to 256,000 I/O operations per second (IOPS). The throughput of io1 volumes varies based on the amount of IOPS provisioned per volume and on the size of the IO operations being executed. For more information about throughput of io1 volumes, see Provisioned IOPS volumes in the Amazon EC2 User Guide.

The following table shows the range of Provisioned IOPS and and maximum throughput for each database engine and storage size range.

Database engine	Range of storage size	Range of Provisioned IOPS	Maximum throughput
MariaDB, MySQL, and PostgreSQL	Between 100 and 399 GiB	1,000–19,950 IOPS	500 MiB/s
MariaDB, MySQL, and PostgreSQL	Between 400 and 65,536 GiB	1,000–256,000 IOPS	4,000 MiB/s
Oracle	Between 100 and 199 GiB	1,000–9,950 IOPS	500 MiB/s
Oracle	Between 200 and 65,536 GiB	1,000–256,000 IOPS	4,000 MiB/s
SQL Server	Between 20 and 16,384 GiB	1,000–64,000 IOPS	1,000 MiB/s

Note

For SQL Server, the maximum 64,000 IOPS is guaranteed only on Nitro-based instances that are on the m5*, m6i, r5*, r6i, and z1d instance types. Other instance types guarantee performance up to 32,000 IOPS.

For Oracle, you can provision the maximum 256,000 IOPS only on the r5b instance type.

The IOPS and storage size ranges have the following constraints:

• The ratio of IOPS to allocated storage (in GiB) must be from 1–50 on RDS for SQL Server, and 0.5–50 on other RDS DB engines.

• If you're using storage autoscaling, the same ratios between IOPS and maximum storage threshold (in GiB) also apply.

  For more information on storage autoscaling, see Managing capacity automatically with Amazon RDS storage autoscaling.

Combining Provisioned IOPS storage with Multi-AZ deployments or read replicas

For production OLTP use cases, we recommend that you use Multi-AZ deployments for enhanced fault tolerance with Provisioned IOPS storage for fast and predictable performance.

You can also use Provisioned IOPS SSD storage with read replicas for MySQL, MariaDB or PostgreSQL. The type of storage for a read replica is independent of that on the primary DB instance. For example, you might use General Purpose SSD for read replicas with a primary DB instance that uses Provisioned IOPS SSD storage to reduce costs. However, your read replica's performance in this case might differ from that of a configuration where both the primary DB instance and the read replicas use Provisioned IOPS SSD storage.

Provisioned IOPS storage costs

With Provisioned IOPS storage, you are charged for the provisioned resources whether or not you use them in a given month.

For more information about pricing, see Amazon RDS pricing.

Getting the best performance from Amazon RDS Provisioned IOPS SSD storage

If your workload is I/O constrained, using Provisioned IOPS SSD storage can increase the number of I/O requests that the system can process concurrently. Increased concurrency allows for decreased latency because I/O requests spend less time in a queue. Decreased latency allows for faster database commits, which improves response time and allows for higher database throughput.

Provisioned IOPS SSD storage provides a way to reserve I/O capacity by specifying IOPS. However, as with any other system capacity attribute, its maximum throughput under load is constrained by the resource that is consumed first. That resource might be network bandwidth, CPU, memory, or database internal resources.

For more information about getting the most out of your Provisioned IOPS volumes, see Amazon EBS volume performance.

Comparing solid-state drive (SSD) storage types

The following table shows use cases and performance characteristics for the SSD storage volumes used by Amazon RDS.

Characteristic	Provisioned IOPS (io1)	General Purpose (gp3)	General Purpose (gp2)
Description	Consistent storage performance (IOPS, throughput, latency) Designed for latency-sensitive, transactional workloads	Flexibility in provisioning storage, IOPS, and throughput independently Balances price performance for a wide variety of transactional workloads	Provides burstable IOPS Balances price performance for a wide variety of transactional workloads
Use cases	Transactional workloads that require sustained IOPS performance up to 256,000 IOPS	Broad range of workloads running on medium-sized relational databases in development/test environments	Broad range of workloads running on medium-sized relational databases in development/test environments
Latency	Single-digit millisecond, provided consistently 99.9% of the time	Single-digit millisecond, provided consistently 99% of the time	Single-digit millisecond, provided consistently 99% of the time
Volume size	100 GiB–64 TiB (16 TiB on RDS for SQL Server)	20 GiB–64 TiB (16 TiB on RDS for SQL Server)	20 GiB–64 TiB (16 TiB on RDS for SQL Server)
Maximum IOPS	256,000 (64,000 on RDS for SQL Server)	64,000 (16,000 on RDS for SQL Server)	64,000 (16,000 on RDS for SQL Server) Note You can't provision IOPS directly on gp2 storage. IOPS varies with the allocated storage size.
Maximum throughput	Scales based on Provisioned IOPS up to 4,000 MB/s	Provision additional throughput up to 4,000 MB/s (1000 MB/s on RDS for SQL Server	1000 MB/s (250 MB/s on RDS for SQL Server)
AWS CLI and RDS API name	io1	gp3	gp2

Magnetic storage

Amazon RDS also supports magnetic storage for backward compatibility. We recommend that you use General Purpose SSD or Provisioned IOPS SSD for any new storage needs. The following are some limitations for magnetic storage:

• Doesn't allow you to scale storage when using the SQL Server database engine.

• Doesn't support storage autoscaling.

• Doesn't support elastic volumes.

• Limited to a maximum size of 3 TiB.

• Limited to a maximum of 1,000 IOPS.

Monitoring storage performance

Amazon RDS provides several metrics that you can use to determine how your DB instance is performing. You can view the metrics on the summary page for your instance in Amazon RDS Management Console. You can also use Amazon CloudWatch to monitor these metrics. For more information, see Viewing metrics in the Amazon RDS console. Enhanced Monitoring provides more detailed I/O metrics; for more information, see Monitoring OS metrics with Enhanced Monitoring.

The following metrics are useful for monitoring storage for your DB instance:

• IOPS – The number of I/O operations completed each second. This metric is reported as the average IOPS for a given time interval. Amazon RDS reports read and write IOPS separately on 1-minute intervals. Total IOPS is the sum of the read and write IOPS. Typical values for IOPS range from zero to tens of thousands per second.

• Latency – The elapsed time between the submission of an I/O request and its completion. This metric is reported as the average latency for a given time interval. Amazon RDS reports read and write latency separately at 1-minute intervals. Typical values for latency are in milliseconds (ms).

• Throughput – The number of bytes each second that are transferred to or from disk. This metric is reported as the average throughput for a given time interval. Amazon RDS reports read and write throughput separately on 1-minute intervals using units of megabytes per second (MB/s). Typical values for throughput range from zero to the I/O channel's maximum bandwidth.

• Queue Depth – The number of I/O requests in the queue waiting to be serviced. These are I/O requests that have been submitted by the application but have not been sent to the device because the device is busy servicing other I/O requests. Time spent waiting in the queue is a component of latency and service time (not available as a metric). This metric is reported as the average queue depth for a given time interval. Amazon RDS reports queue depth in 1-minute intervals. Typical values for queue depth range from zero to several hundred.

Measured IOPS values are independent of the size of the individual I/O operation. This means that when you measure I/O performance, make sure to look at the throughput of the instance, not simply the number of I/O operations.

Factors that affect storage performance

System activities, database workload, and DB instance class can affect storage performance.

System activities

The following system-related activities consume I/O capacity and might reduce DB instance performance while in progress:

• Multi-AZ standby creation

• Read replica creation

• Changing storage types

Database workload

In some cases, your database or application design results in concurrency issues, locking, or other forms of database contention. In these cases, you might not be able to use all the provisioned bandwidth directly. In addition, you might encounter the following workload-related situations:

• The throughput limit of the underlying instance type is reached.

• Queue depth is consistently less than 1 because your application isn't driving enough I/O operations.

• You experience query contention in the database even though some I/O capacity is unused.

In some cases, there isn't a system resource that is at or near a limit, and adding threads doesn't increase the database transaction rate. In such cases, the bottleneck is most likely contention in the database. The most common forms are row lock and index page lock contention, but there are many other possibilities. If this is your situation, seek the advice of a database performance tuning expert.

DB instance class

To get the most performance out of your Amazon RDS DB instance, choose a current generation instance type with enough bandwidth to support your storage type. For example, you can choose Amazon EBS–optimized instances and instances with 10-gigabit network connectivity.

Important

Depending on the instance class you're using, you might see lower IOPS performance than the maximum that you can provision with RDS. For specific information on IOPS performance for DB instance classes, see Amazon EBS–optimized instances in the Amazon EC2 User Guide. We recommend that you determine the maximum IOPS for the instance class before setting a Provisioned IOPS value for your DB instance.

We encourage you to use the latest generation of instances to get the best performance. Previous generation DB instances can also have lower maximum storage.

Some older 32-bit file systems might have lower storage capacities. To determine the storage capacity of your DB instance, you can use the describe-valid-db-instance-modifications AWS CLI command.

The following list shows the maximum storage that most DB instance classes can scale to for each database engine:

• MariaDB – 64 TiB

• Microsoft SQL Server – 16 TiB

• MySQL – 64 TiB

• Oracle – 64 TiB

• PostgreSQL – 64 TiB

The following table shows some exceptions for maximum storage (in TiB). All RDS for Microsoft SQL Server DB instances have a maximum storage of 16 TiB, so there are no entries for SQL Server.

Instance class	MariaDB	MySQL	Oracle	PostgreSQL
db.m3 – standard instance classes
db.m3.2xlarge	N/A	6	N/A	6
db.m3.xlarge	N/A	6	N/A	6
db.m3.large	N/A	6	N/A	6
db.m3.medium	N/A	32	N/A	32
db.t4g – burstable-performance instance classes
db.t4g.medium	16	16	N/A	32
db.t4g.small	16	16	N/A	16
db.t4g.micro	6	6	N/A	6
db.t3 – burstable-performance instance classes
db.t3.medium	16	16	32	32
db.t3.small	16	16	32	16
db.t3.micro	6	6	32	6
db.t2 – burstable-performance instance classes
db.t2.medium	32	32	N/A	32
db.t2.small	16	16	N/A	16
db.t2.micro	6	6	N/A	6

For more details about all instance classes supported, see Previous generation DB instances.