SQL Job being blocked by Commvault Backup

Last post 06-30-2020, 12:52 PM by sekreber. 6 replies.
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  • SQL Job being blocked by Commvault Backup
    Posted: 06-23-2020, 8:58 AM

    I have a unique and inconsistent issue. I have several SQL Servers that we do VMDK backups on. I have the drives that contain SQL DB's filtered out. So, I am only doing the C:\ drive, and in some cases the D:\ drive which is just program data. Our SQL Team reserves other drives for their DB's and Logs. My issue is, if i am only doing the C:\ drive and have SQL Drives excluded, how can the Commvault snapshot and backup of the VMDK cause a blocking issue with their SQL DB. And, this issue isn't consistent. It happened two days in a row last week, then ran fine two days and occured again. We had 25 successfuly daily backups before this started occuring as well. If you need any additional data, please let me know and I will provide it.


    Ed Reber
  • Re: SQL Job being blocked by Commvault Backup
    Posted: 06-23-2020, 9:03 AM

    Hi Sekreber,

    If you're doing an Application Consistent (i.e. quiesced) snapshot, then it might be trying to reach out via VMWare Tools to quiesce the DBs. Can you see if there are I/O freezes and thaws for the SQL DBs registered in the Windows Application Logs?

    David

  • Re: SQL Job being blocked by Commvault Backup
    Posted: 06-23-2020, 9:22 AM

    Hi David,

    The only thing I see in the application log on the Windows server is where the SQL DBA killed the process. I am attaching the screen shot he made of the error before he killed it in SQL.



    Ed Reber
    Attachment: SQL Error.jpg
  • Re: SQL Job being blocked by Commvault Backup
    Posted: 06-23-2020, 9:51 AM

    That is consistent with what you would see if you were to take a quiesced snapshot with the VSA. If you try running with a crash consistent snap instead do you see the same behaviour in SQL Server?

    David

  • Re: SQL Job being blocked by Commvault Backup
    Posted: 06-23-2020, 10:41 AM

    Thank you. When we put the Commvault system in at the end of January, the Engineer I was working with suggested that we do all backups as File System and Application consistent. At the time he was against Crash Consistent. Does crash consistent mount the VM to take the snapshot then unmount it? Would this cause any interruption in the VM that is running? We want to make sure we do not cause outages with our backups. We ran into something like that with our POC of another product. It would mount the VM, snap it and release. When it released the server, it caused issues on some servers. If you can give me the pros and cons of Crash Consistent that you have experienced, it would help us in making the decision.


    Ed Reber
  • Re: SQL Job being blocked by Commvault Backup
    Posted: 06-24-2020, 4:42 AM

    The crash consistent should have less impact than and App Consistent snapshot on the client. Is this an Intellisnap backup or just streaming VSA? There shouldn't be a need to mount the VM on streaming backup. Suggest flipping it to crash consistent and seeing whether it resolves the issue your DBAs are seeing.

    The pros of App Consistent is that the VM backup will reachout and quiesce everything in the VM in order to get a consistent snapshot to restore from if required (hence why it's taking a SQL Backup). Crash Consistent will allow you to restore the VM from backup, but will not guarantee any applications running on it at the time (i.e. SQL Server) will be in a consistent state. 

    It's the equivalent of running a hypervisor level snapshot for a VM with the "Quiesce guest file system" option enabled or not.

    David

  • Re: SQL Job being blocked by Commvault Backup
    Posted: 06-30-2020, 12:52 PM

    Crash Consistent does solve this issue. Thank yoiu for the solkution. We are probably going to do file level because of the SQL Admins preference.


    Ed Reber
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