# Multi AZ

We use this concept to handle disaster recovery to make our DB more high availability.

It will have  another DB called `standby` DB that **synchronized** data from`master` DB so when the `master` DB is failed , It used `standby` DB to recovery process . (`Read replica` can be used as `standby` DB). Application used one DNS name to connect with DB so in case that `master` DB failed it will automatic failover to connect `standby` DB.

<img src="https://2166680554-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FP9VzT74ziIucCaJgfreE%2Fuploads%2FrbsstwBpsof4euXl51xo%2Ffile.excalidraw.svg?alt=media&#x26;token=cd0481bb-1d8d-4102-92fa-e1000170d427" alt="" class="gitbook-drawing">

#### From Single AZ to Multi AZ (!Important)

It has zero down time operation to move DB from single AZ to multi AZ. Firstly It creates a snapshot for `master`   DB  next It restore DB in new AZ from snapshot and establish **sync** connection from `master` to this new DB.<br>

<img src="https://2166680554-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FP9VzT74ziIucCaJgfreE%2Fuploads%2F3WWD2Opoa7FowOjktCIR%2Ffile.excalidraw.svg?alt=media&#x26;token=9c7b3c52-f2a0-42d6-a911-244ddd3e3257" alt="" class="gitbook-drawing">