How to read Azure ZRS blob is primary zone has failed.

  • 7 February 2023
  • 1 reply

Badge +4

I’m looking for some guidance or documentation on what can be done with ZRS storage. 

Say we have the following availability zones in the region.

Zone 1: Media Agents and Hot blob backing up local VM’s, files etc. no Aux copy.

Zone 2: Standby Media Agent and conserve powered down. Commsere DR recovery done manually. 


Zone1 failed so we power up MA and CS at Zone2 - perform manual DR backup set restore 

Next step - getting the ZRS storage mounted as primary. - any links, docs steps would be much appreciated.












Best answer by Damian Andre 7 February 2023, 23:47

View original

1 reply

Userlevel 7
Badge +23

Hey @RobsterFine 

My understanding is that they way we access storage is agnostic to us. Meaning - if a zone fails azure will serve us up a copy from a working copy in another availability zone. This is supported by the Azure docs:

With ZRS, your data is still accessible for both read and write operations even if a zone becomes unavailable. If a zone becomes unavailable, Azure undertakes networking updates, such as DNS repointing. These updates may affect your application if you access data before the updates have completed. When designing applications for ZRS, follow practices for transient fault handling, including implementing retry policies with exponential back-off.


So as soon as Microsoft updates the DNS to point to the good zone, Commvault can resume like nothing happened.

In terms of design, that just means you can connect all your media agents to the same cloud library. If you start a Media Agent in another zone then it can resume recovery operations as long as its shared in the storage policy (or plan) and cloud library. Backups may be more difficult as deduplication could be involved and you may need to move / reconstruct the database to continue that.


If only the storage failed in the zone (and not the compute) then I would expect things to function pretty transparently, unless it takes Microsoft a long time to point to an alternative zone.