Amazon Redshift snapshots and backups

Snapshots are point-in-time backups of a cluster. There are two types of snapshots: automated and manual. Amazon Redshift stores these snapshots internally in Amazon S3 by using an encrypted Secure Sockets Layer (SSL) connection.

Amazon Redshift automatically takes incremental snapshots that track changes to the cluster since the previous automated snapshot. Automated snapshots retain all of the data required to restore a cluster from a snapshot. You can create a snapshot schedule to control when automated snapshots are taken, or you can take a manual snapshot any time.

When you restore from a snapshot, Amazon Redshift creates a new cluster and makes the new cluster available before all of the data is loaded, so you can begin querying the new cluster immediately. The cluster streams data on demand from the snapshot in response to active queries, then loads the remaining data in the background.

When you launch a cluster, you can set the retention period for automated and manual snapshots. You can change the default retention period for automated and manual snapshots by modifying the cluster. You can change the retention period for a manual snapshot when you create the snapshot or by modifying the snapshot.

You can monitor the progress of snapshots by viewing the snapshot details in the AWS Management Console, or by calling describe-cluster-snapshots in the CLI or the DescribeClusterSnapshots API action. For an in-progress snapshot, these display information such as the size of the incremental snapshot, the transfer rate, the elapsed time, and the estimated time remaining.

To ensure that your backups are always available to your cluster, Amazon Redshift stores snapshots in an internally managed Amazon S3 bucket that is managed by Amazon Redshift. To manage storage charges, evaluate how many days you need to keep automated snapshots and configure their retention period accordingly. Delete any manual snapshots that you no longer need. For more information about the cost of backup storage, see the Amazon Redshift pricing page.

Working with snapshots and backups in Amazon Redshift Serverless

Amazon Redshift Serverless, like a provisioned cluster, enables you to take a backup as a point-in-time representation of the objects and data in the namespace. There are two types of backups in Amazon Redshift Serverless: snapshots that are manually created and recovery points that Amazon Redshift Serverless creates automatically. You can find more information about working with snapshots for Amazon Redshift Serverless at Snapshots and recovery points.

You can also restore a snapshot from a provisioned cluster to a serverless namespace. For more information, see Restoring a serverless namespace from a snapshot.

Automated snapshots

When automated snapshots are enabled for a cluster, Amazon Redshift periodically takes snapshots of that cluster. By default Amazon Redshift takes a snapshot about every eight hours or following every 5 GB per node of data changes, or whichever comes first. If your data is larger than 5 GB * the number of nodes, the shortest amount of time in between automated snapshot creation is 15 minutes. Alternatively, you can create a snapshot schedule to control when automated snapshots are taken. If you're using custom schedules, the minimum amount of time between automated snapshots is one hour. Automated snapshots are enabled by default when you create a cluster.

Automated snapshots are deleted at the end of a retention period. The default retention period is one day, but you can modify it by using the Amazon Redshift console or programmatically by using the Amazon Redshift API or CLI.

To disable automated snapshots, set the retention period to zero. If you disable automated snapshots, Amazon Redshift stops taking snapshots and deletes any existing automated snapshots for the cluster. You can't disable automated snapshots for RA3 node types. You can set an RA3 node type automated retention period from 1–35 days.

Only Amazon Redshift can delete an automated snapshot; you cannot delete them manually. Amazon Redshift deletes automated snapshots at the end of a snapshot's retention period, when you disable automated snapshots for the cluster, or when you delete the cluster. Amazon Redshift retains the latest automated snapshot until you disable automated snapshots or delete the cluster.

If you want to keep an automated snapshot for a longer period, you can create a copy of it as a manual snapshot. The automated snapshot is retained until the end of the retention period, but the corresponding manual snapshot is retained until you manually delete it or until the end of the retention period.

Automated snapshot schedules

To precisely control when snapshots are taken, you can create a snapshot schedule and attach it to one or more clusters. When you modify a snapshot schedule, the schedule is modified for all associated clusters. If a cluster doesn't have a snapshot schedule attached, the cluster uses the default automated snapshot schedule.

A snapshot schedule is a set of schedule rules. You can define a simple schedule rule based on a specified interval, such as every 8 hours or every 12 hours. You can also add rules to take snapshots on certain days of the week, at specific times, or during specific periods. Rules can also be defined using Unix-like cron expressions.

Snapshot schedule format

On the Amazon Redshift console, you can create a snapshot schedule. Then, you can attach a schedule to a cluster to trigger the creation of a system snapshot. A schedule can be attached to multiple clusters, and you can create multiple cron definitions in a schedule to trigger a snapshot.

You can define a schedule for your snapshots using a cron syntax. The definition of these schedules uses a modified Unix-like cron syntax. You specify time in Coordinated universal time (UTC). You can create schedules with a maximum frequency of one hour and minimum precision of one minute.

Amazon Redshift modified cron expressions have 3 required fields, which are separated by white space.

Syntax

cron(Minutes Hours Day-of-month Month Day-of-week Year)

Fields	Values	Wildcards
Minutes	0–59	, - * /
Hours	0–23	, - * /
Day-of-month	1–31	, - * ? / L W
Month	1–12 or JAN-DEC	, - * /
Day-of-week	1–7 or SUN-SAT	, - * ? L #
Year	1970–2199	, - * /

Wildcards

• The , (comma) wildcard includes additional values. In the Day-of-week field, MON,WED,FRI would include Monday, Wednesday, and Friday. Total values are limited to 24 per field.

• The - (dash) wildcard specifies ranges. In the Hour field, 1–15 would include hours 1 through 15 of the specified day.

• The * (asterisk) wildcard includes all values in the field. In the Hours field, * would include every hour.

• The / (forward slash) wildcard specifies increments. In the Hours field, you could enter 1/10 to specify every 10th hour, starting from the first hour of the day (for example, the 01:00, 11:00, and 21:00).

• The ? (question mark) wildcard specifies one or another. In the Day-of-month field you could enter 7, and if you didn't care what day of the week the seventh was, you could enter ? in the Day-of-week field.

• The L wildcard in the Day-of-month or Day-of-week fields specifies the last day of the month or week.

• The W wildcard in the Day-of-month field specifies a weekday. In the Day-of-month field, 3W specifies the day closest to the third weekday of the month.

• The # wildcard in the Day-of-week field specifies a certain instance of the specified day of the week within a month. For example, 3#2 would be the second Tuesday of the month: the 3 refers to Tuesday because it is the third day of each week, and the 2 refers to the second day of that type within the month.

  Note

  If you use a '#' character, you can define only one expression in the day-of-week field. For example, "3#1,6#3" is not valid because it is interpreted as two expressions.

Limits

• You can't specify the Day-of-month and Day-of-week fields in the same cron expression. If you specify a value in one of the fields, you must use a ? (question mark) in the other.

• Snapshot schedules don't support the following frequencies:

  • Snapshots scheduled more frequently than 1 per hour.

  • Snapshots scheduled less frequently than 1 per day (24 hours).

  If you have overlapping schedules that result in scheduling snapshots within a 1 hour window, a validation error results.

When creating a schedule, you can use the following sample cron strings.

Minutes	Hours	Day of week	Meaning
0	14-20/1	TUE	Every hour between 2pm and 8pm on Tuesday.
0	21	MON-FRI	Every night at 9pm Monday–Friday.
30	0/6	SAT-SUN	Every 6 hour increment on Saturday and Sunday starting at 30 minutes after midnight (00:30) that day. This results in a snapshot at [00:30, 06:30, 12:30, and 18:30] each day.
30	12/4	*	Every 4 hour increment starting at 12:30 each day. This resolves to [12:30, 16:30, 20:30].

For example to run on a schedule on an every 2 hour increment starting at 15:15 each day. This resolves to [15:15, 17:15, 19:15, 21:15, 23:15] , specify:

cron(15 15/2 *)   

You can create multiple cron schedule definitions within as schedule. For example the following AWS CLI command contains two cron schedules in one schedule.

create-snapshot-schedule --schedule-identifier "my-test" --schedule-definition "cron(0 17 SAT,SUN)" "cron(0 9,17 MON-FRI)"   

Manual snapshots

You can take a manual snapshot any time. By default, manual snapshots are retained indefinitely, even after you delete your cluster. You can specify the retention period when you create a manual snapshot, or you can change the retention period by modifying the snapshot. For more information about changing the retention period, see Modifying the manual snapshot retention period.

If a snapshot is deleted, you can't start any new operations that reference that snapshot. However, if a restore operation is in progress, that restore operation will run to completion.

Amazon Redshift has a quota that limits the total number of manual snapshots that you can create; this quota is per AWS account per AWS Region. The default quota is listed at Quotas and limits in Amazon Redshift.

Snapshot storage

Because snapshots accrue storage charges, it's important that you delete them when you no longer need them. Amazon Redshift deletes automated and manual snapshots at the end of their respective snapshot retention periods. You can also delete manual snapshots using the AWS Management Console or with the batch-delete-cluster-snapshots CLI command.

You can change the retention period for a manual snapshot by modifying the manual snapshot settings.

You can get information about how much storage your snapshots are consuming using the Amazon Redshift Console or using the describe-storage CLI command.

Excluding tables from snapshots

By default, all user-defined permanent tables are included in snapshots. If a table, such as a staging table, doesn't need to be backed up, you can significantly reduce the time needed to create snapshots and restore from snapshots. You also reduce storage space on Amazon S3 by using a no-backup table. To create a no-backup table, include the BACKUP NO parameter when you create the table. For more information, see CREATE TABLE and CREATE TABLE AS in the Amazon Redshift Database Developer Guide.