High Availability for Azure Managed Cache Service
Important
Microsoft recommends all new developments use Azure Redis Cache. For current documentation and guidance on choosing an Azure Cache offering, see Which Azure Cache offering is right for me?
Microsoft Azure Cache allows you to maintain high availability for cached objects. With high availability, cached objects are replicated within the cache for resiliency against hardware failure. High availability is configured at the named cache level in the Management Portal on the Configure tab for Cache. No code changes are required; you need only to recalculate the required memory capacity for your workload. This can be done by turning on the High Availability setting in the capacity planning spreadsheet. For more information, see Capacity Planning for Azure Managed Cache Service.
Note
High availability is only available in the Standard and Premium cache offerings, and is not available in the Basic cache offering. For more information, see Cache Offerings for Azure Managed Cache Service.
About High Availability
When high availability is enabled, a second copy of each cached item is maintained. That way if a part of the cache service goes down, a backup copy still exists. In this scenario, the secondary copy is promoted to the primary copy. A new secondary copy is then to maintain high availability. During this interval, there may be a short period of time where secondary copies are promoted to primary copies and routing information is updated. During that time, clients may receive DataCacheException exceptions with an ErrorCode of RetryLater. caching applications should use normal error handling and retry logic to correctly react to this condition.
In order to implement high availability, all cache writes are made to both the primary and secondary copies.
Because all writes are made to both the primary and secondary copies, high availability increases latency and decreases throughput. This can be a reasonable trade-off for caches that benefit from high availability.
By definition, the use of high availability multiplies the amount of required memory for each cached item by two. Consider this memory impact during capacity planning tasks. For more information, see Capacity Planning for Azure Managed Cache Service.
High availability is only available in the Standard and Premium cache offerings, and is not available in the Basic cache offering. For more information, see Cache Offerings for Azure Managed Cache Service.
To Enable High Availability
High availability is configured at the named cache level in the Management Portal on the Configure tab for Cache. The default setting for high availability is Disabled.
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Note
If you have the Basic cache offering, the High Availability column will not be displayed in the Named Caches section of the Configure tab.