DR recovery question. Say we lost the last few days of backups.

Last post 10-01-2020, 5:02 PM by mstruening. 5 replies.
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  • DR recovery question. Say we lost the last few days of backups.
    Posted: 10-01-2020, 1:15 PM

    Playing out the worse case scenario and hoping it does not happen.  Say we lost all infrastrcture. Commserve, MAs, everything.  Also assume we lost the last few days of backups, but have everything older then 2 days on disk due to hardware snapshots/3rd tier storage. This is not counting the Commvault DR backup as that is small can be air gapped. 

    So I fire up a the cold DR infranstructore with Commserve and MA, and load the latest DR backup into the DR Commserve. I change the library location to point to the backup storage.  Some config changes later, I should beable to start restoring VMs. 

    But how does Commvault know we lost 2 days of backups? Do I just only restore backups from 2 days ago and ignore the newer ones? 

     

     

     

     

  • Re: DR recovery question. Say we lost the last few days of backups.
    Posted: 10-01-2020, 2:39 PM

    Good question.  

    If the database is from 2 days ago, then (in theory) the Job IDs in the database should match what is actualy there, depending on how close the DR backup was taken compared to when disaster struck (and how many, if any jobs ran in between).

    To clarify, are you restoring a CS DR backup from <now> or from 2 days ago?

    Meaning, what jobs will this CS database 'think' exist?

    Adding this link as it likely applies:

    https://documentation.commvault.com/commvault/v11/article?p=12371.htm

  • Re: DR recovery question. Say we lost the last few days of backups.
    Posted: 10-01-2020, 3:40 PM

    So working with what we currently have, the main backup target/library is shared with other systems. I can't protect it as much as I would like. 

    The CS DR backup is much smaller, and I can store it on different and much better protected storage. I can have it sitting on the same server running the cold DR CS and MA for a "DR recovery in a box" all ready to go. The entire network could be down, and I can plug a monitor into this and have it ready when the network is back up. 

    So the CS DR would be from the last backup, aka <now>.  The Library may be out of date by several days. Depending on hardware snapshots or storage based syncing to an off site copy. 

    I could run a verification job and purge backups that fail, but when we are doing an DR recovery, that might be time wasted.

    So the question is, will Commvault see the the discrepancy from the CS DR backup, and what is on the Library and prevent me from selecting 50VM backups from last week and blasting them into a fresh ESXi host? 

     

     

     

     

     

  • Re: DR recovery question. Say we lost the last few days of backups.
    Posted: 10-01-2020, 3:50 PM

    Appreciate the extra context.

    in essence, no.  the CommServe will think that data is there (unless you rtun a Data Verification, which run against a Cloud library might incur charges, FYI).

    What you would do is browse and restore by Job ID from a range where you know these jobs are valid.

    Now, if you have Aux Copies of the data going to Tape (or anywhere else, really) and those libraries are safe from this disaster, then you would be 100% fine (persuant to the Aux copies being caught up, etc.).

    The only way for the CS to 'know' what is valid or not would be to look at the actual data compared to the job IDs in the database and verify that the Archive files (that make up the jobs) are physically there, which is what a DV does.  As you noted, it's a time consuming process if done at a large scale, so you only do it when you need to like this situation.

    Let me know if that clarifies things for you!

  • Re: DR recovery question. Say we lost the last few days of backups.
    Posted: 10-01-2020, 4:09 PM

    That is exactly how I suspected it would work, but I have not tried it (yet). I was hoping there was nothing I was missing that would make this plan a show stopper.  Aux copy is in the works. 

    Thanks for the help. 

  • Re: DR recovery question. Say we lost the last few days of backups.
    Posted: 10-01-2020, 5:02 PM

    My pleasure!

    Feel free to mark the post as solved for anyone else who might have a simialr question.

    Thanks!!

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