Amazon ElastiCache for Redis | Backup and Restore Flashcards
Can I test the Multi-AZ functionality?
Backup and Restore
Amazon ElastiCache for Redis | Database
Yes. If you have the “Multi-AZ” feature enabled on a cluster or replication group with one or more read replicas, you can trigger a failover. ElastiCache will respond in the same way as a real failure scenario – by detecting the failure, promoting the most up-to-date read replica to become the new primary, and then replacing the failed primary, attaching it as a new read replica in place of the one promoted. For more details on testing failover, please see documentation.
What is Backup and Restore?
Backup and Restore
Amazon ElastiCache for Redis | Database
Backup and Restore is a feature that allows customers to create snapshots of their ElastiCache for Redis clusters. ElastiCache stores the snapshots, allowing users to subsequently use them to restore Redis clusters.
What is a snapshot?
Backup and Restore
Amazon ElastiCache for Redis | Database
A snapshot is a copy of your entire Redis cluster at a specific moment.
Why would I need snapshots?
Backup and Restore
Amazon ElastiCache for Redis | Database
Creating snapshots can be useful in case of data loss caused by node failure, as well as the unlikely event of a hardware failure. Another common reason to use backups is for archiving purposes. Snapshots are stored in Amazon S3, which is a durable storage, meaning that even a power failure won’t erase your data.
What can I do with a snapshot?
Backup and Restore
Amazon ElastiCache for Redis | Database
You can use snapshots to warm start an ElastiCache for Redis cluster with preloaded data.
How does Backup and Restore work?
Backup and Restore
Amazon ElastiCache for Redis | Database
When a backup is initiated, ElastiCache will take a snapshot of a specified Redis cluster that can later be used for recovery or archiving. You can initiate a backup anytime you choose or set a recurring daily backup with retention period of up to 35 days.
When you choose a snapshot to restore, a new ElastiCache for Redis cluster will be created and populated with the snapshot’s data. This way you can create multiple ElastiCache for Redis clusters from a specified snapshot.
Currently, ElastiCache uses Redis’ native mechanism to create and store an RDB file as the snapshot.
Where are my snapshots stored?
Backup and Restore
Amazon ElastiCache for Redis | Database
The snapshots are stored in S3.
How can I get started using Backup and Restore?
Backup and Restore
Amazon ElastiCache for Redis | Database
You can select to use the Backup and Restore feature through the AWS Management Console, through the ElastiCache APIs (CreateCacheCluster, ModifyCacheCluster and ModifyReplicationGroup API’s) and CLI. You can deactivate and reactivate the feature anytime you choose.
How do I specify which Redis cluster and node to backup?
Backup and Restore
Amazon ElastiCache for Redis | Database
Backup and Restore creates snapshots on a cluster basis. Users can specify which ElastiCache for Redis cluster to backup through the AWS Management Console, CLI or through the CreateSnapshot API. In a Replication Group, you can choose to backup the primary or any of the read-replica clusters. We recommend users enable backup on one of the read-replicas, mitigating any latency effect on the Redis primary.
Does ElastiCache for Memcached support Backup and Restore?
Backup and Restore
Amazon ElastiCache for Redis | Database
No, snapshots are available only for ElastiCache for Redis.
How can I specify when a backup will take place?
Backup and Restore
Amazon ElastiCache for Redis | Database
Through the AWS Management Console, CLI or APIs you can specify when to start a single backup or a recurring backup. Users are able to:
Take a snapshot right now (through “Backup” console button in the “Redis” tab, or CreateSnapshot API)
Set up an automatic daily backup. The backup will take place during your preferred backup window. You can set that up through Creating/Modifying cluster via console or the CreateCacheCluster, ModifyCacheCluster or ModifyReplicationGroup API’s.
What is a backup window and why do I need it?
Backup and Restore
Amazon ElastiCache for Redis | Database
The preferred backup window is the user-defined period of time during which your ElastiCache for Redis cluster backup will start. This is helpful if you want to backup at a certain time of day or to refrain from backups during a particularly high-utilization period.
What is the performance impact of taking a snapshot?
Backup and Restore
Amazon ElastiCache for Redis | Database
While taking a snapshot, you may encounter increased latencies for a brief period at the node. Snapshots use Redis’s built-in BGSAVE and are subject to its strengths and limitations. In particular, the Redis process forks and the parent continues to serve requests while the child saves the data on disk and then exits. The forking increases the memory usage for the duration of the snapshot generation. When this memory usage exceeds that of the available memory of the node, swapping can get triggered, further slowing down the node. For this reason, we recommend generating snapshots on one of the read replicas (instead of the primary). Also, we suggest setting the reserved-memory parameter to minimize swap usage. See here for more details.
Can I create a snapshot from an ElastiCache for Redis read replica?
Backup and Restore
Amazon ElastiCache for Redis | Database
Yes. Creating a snapshot from a read replica is the best way to backup your data while minimizing performance impact.
In what regions is the Backup and Restore feature available?
Backup and Restore
Amazon ElastiCache for Redis | Database
Backup and Restore feature is available in all regions where ElastiCache service is available.
