Elasticache migration from one account to another

Question

I have an Elasticache running on Redis engine (version 5.0.6), with 1 node and cluster mode and multi-az modes disabled. I want to migrate the Elasticache from this account to another account. I looked up several articles which say to create a backup of Elasticache and use an s3 bucket to send the backup to the target account. However, I don't want to use this method as I will possibly have to take multiple snapshots of the existing Elasticache Redis. 
I asked gpt4 and it suggested using the live replication method. But I don't seem to find any article or documentation about it. But this method seems good as it will continuously replicate new data from the old Elasticache to the new one until I decommission the old one from production. Help me to find an easy and cost-effective approach for this migration.
PS: I am no expert in Redis and Elasticache. If I need any prior knowledge let me know about that too.

Pandurangaswamy · Answer

Hi rafid,

Please try this below solution.

**Step-by-Step Guide for Migrating ElastiCache Redis Between AWS Accounts Using Live Replication**

**Set Up the Target ElastiCache Redis Instance:**

* In the target AWS account, create a new ElastiCache Redis instance with the same configuration as the source instance (version, node type, etc.).

https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/Clusters.Create.html

**Enable Access Between Accounts:**

* Ensure the source and target ElastiCache instances can communicate. This may involve setting up VPC peering or using Transit Gateway.
* Update the security groups and network ACLs to allow traffic between the instances on port 6379.

https://docs.aws.amazon.com/vpc/latest/peering/what-is-vpc-peering.html

https://docs.aws.amazon.com/vpc/latest/tgw/what-is-transit-gateway.html

https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/WhatIs.html

**Configure Source Redis as Master and Target Redis as Slave:**

* Connect to the target Redis instance using the Redis CLI or a similar tool.
* Run the SLAVEOF command on the target instance to make it a replica of the source instance:

```
redis-cli -h  -p 6379
SLAVEOF  6379

```
**Monitor Replication:**

* Monitor the replication process to ensure data is being copied correctly. Use the INFO REPLICATION command:

```

redis-cli -h  -p 6379
INFO REPLICATION
```

**Cutover and Promote the Target:**

* Once ready to switch to the new instance, promote the target Redis instance to master:

```
redis-cli -h  -p 6379
SLAVEOF NO ONE
```
Update your applications to connect to the new Redis instance.

**Decommission the Old Instance:**

* After verifying the new instance is working correctly, decommission the old Redis instance.

https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/Clusters.Delete.html

**Prerequisites and Considerations**

**1. Basic Redis Knowledge:**

* Understand Redis replication concepts, master-slave architecture, and relevant commands (SLAVEOF, INFO REPLICATION).
* Redis Documentation

**2. Network Configuration:**

* Familiarize yourself with VPC peering, security groups, and network ACLs to enable communication between instances in different AWS accounts.
* VPC Peering
* Security Groups

3. Monitoring and Maintenance:

* Monitor the replication process and troubleshoot any issues such as network latency or replication lag.

https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/CacheMetrics.WhichShouldIMonitor.html

**4. Testing:**

* Test the entire process in a staging environment before performing the migration in production to identify any potential issues.

Elasticache migration from one account to another

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