Azure Redis Cache has different cache offerings which provide flexibility in the choice of cache size and features, including Premium tier features such as clustering, persistence, and virtual network support. This article describes how to configure persistence in a premium Azure Redis Cache instance.
For information on other premium cache features, see Introduction to the Azure Redis Cache Premium tier.
What is data persistence?
Redis persistence allows you to persist data stored in Redis. You can also take snapshots and back up the data, which you can load in case of a hardware failure. This is a huge advantage over Basic or Standard tier where all the data is stored in memory and there can be potential data loss in case of a failure where Cache nodes are down.
Azure Redis Cache offers Redis persistence using the RDB model, where the data is stored in an Azure storage account. When persistence is configured, Azure Redis Cache persists a snapshot of the Redis cache in a Redis binary format to disk based on a configurable backup frequency. If a catastrophic event occurs that disables both the primary and replica cache, the cache is reconstructed using the most recent snapshot.
Persistence can be configured from the New Redis Cache blade during cache creation and on the Resource menu for existing premium caches.
To create a premium cache, sign-in to the Azure portal and click New > Databases > Redis Cache.
In addition to creating caches in the Azure portal, you can also create them using Resource Manager templates, PowerShell, or Azure CLI. For more information about creating an Azure Redis Cache, see Create a cache.
To configure premium features, first select one of the premium pricing tiers in the Pricing tier drop-down list. For more information about each pricing tier, click View full pricing details and select a pricing tier from the Choose your pricing tier blade.
Once a premium pricing tier is selected, click Redis persistence.
The steps in the following section describe how to configure Redis persistence on your new premium cache. Once Redis persistence is configured, click Create to create your new premium cache with Redis persistence.
Configure Redis persistence
Redis persistence is configured on the Redis data persistence blade. For new caches, this blade is accessed during the cache creation process, as described in the previous section. For existing caches, the Redis data persistence blade is accessed from the Resource menu for your cache.
To enable Redis persistence, click Enabled to enable RDB (Redis database) backup. To disable Redis persistence on a previously enabled premium cache, click Disabled.
To configure the backup interval, select a Backup Frequency from the drop-down list. Choices include 15 Minutes, 30 minutes, 60 minutes, 6 hours, 12 hours, and 24 hours. This interval starts counting down after the previous backup operation successfully completes and when it elapses a new backup is initiated.
Click Storage Account to select the storage account to use, and choose either the Primary key or Secondary key to use from the Storage Key drop-down. You must choose a storage account in the same region as the cache, and a Premium Storage account is recommended because premium storage has higher throughput.
If the storage key for your persistence account is regenerated, you must reconfigure the desired key from the Storage Key drop-down.
Click OK to save the persistence configuration.
The next backup (or first backup for new caches) is initiated once the backup frequency interval elapses.
The following list contains answers to commonly asked questions about Azure Redis Cache persistence.
- Can I enable persistence on a previously created cache?
- Can I change the backup frequency after I create the cache?
- Why if I have a backup frequency of 60 minutes there is more than 60 minutes between backups?
- What happens to the old backups when a new backup is made?
- What happens if I have scaled to a different size and a backup is restored that was made before the scaling operation?
Can I enable persistence on a previously created cache?
Yes, Redis persistence can be configured both at cache creation and on existing premium caches.
Can I change the backup frequency after I create the cache?
Yes, you can change the backup frequency on the Redis data persistence blade. For instructions, see Configure Redis persistence.
Why if I have a backup frequency of 60 minutes there is more than 60 minutes between backups?
The backup frequency interval does not start until the previous backup process has completed successfully. If the backup frequency is 60 minutes and it takes a backup process 15 minutes to successfully complete, the next backup won't start until 75 minutes after the start time of the previous backup.
What happens to the old backups when a new backup is made?
All backups except for the most recent one are automatically deleted. This deletion may not happen immediately but older backups are not persisted indefinitely.
What happens if I have scaled to a different size and a backup is restored that was made before the scaling operation?
- If you have scaled to a larger size, there is no impact.
- If you have scaled to a smaller size, and you have a custom databases setting that is greater than the databases limit for your new size, data in those databases isn't be restored. For more information, see Is my custom databases setting affected during scaling?
- If you have scaled to a smaller size, and there isn't enough room in the smaller size to hold all of the data from the last backup, keys will be evicted during the restore process, typically using the allkeys-lru eviction policy.
Learn how to use more premium cache features.