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SQL Locks

carl.fedak
over 6 years ago

Hello,

 

We are using MSSQL 2014, and RR 6.1.1.137.

Our database server has C (170GB), D (2.2 TB), E (360GB), F (5.6TB).

Currently all databases are set to simple recovery, and our schedule is set to 2 hours.

Unfortunately, at least once a day we have a period where our application (custom built .NET web app) throws a bunch of errors saying it cannot write to the database, we are getting locks.  These are happening only at scheduled backup times, and typically when that happens we have 2-3 retries of the backups.

This is, of course, causing client impact.

Our database is not particularly busy, I feel like maybe we are just doing something wrong or Rapid Recovery would never really work for live databases.  In which case I'm unsure how they could be selling it.

One suspicion, we do have some fairly long running transactions in the application.  These are not changeable at this time.  Could this be causing issues like I've mentioned where DB locks are occurring?

 

Looking for any tips at all.

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  • 0 over 6 years ago
    Just to add to the conversation -- VSS locks only WRITE IOs; READ IOs continue to work.
    The issue may be related to the number (or size) of the databases as there are hard limitations for both as of what VSS can handle.
    If the databases (and logs) are spread over multiple volumes, I would suggest attempting to backup the volume pairs databases+logs separately. For instance if C: is the system volume D: contains some databases and their logs and E: contains databases and F: contains the logs for the databases on E:, back up C; separately, D: separately and E: and F: separately (at 30 min intervals for instance). This would reduce the time the SQLWriter needs to freeze various databases.
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  • 0 over 6 years ago
    Just to add to the conversation -- VSS locks only WRITE IOs; READ IOs continue to work.
    The issue may be related to the number (or size) of the databases as there are hard limitations for both as of what VSS can handle.
    If the databases (and logs) are spread over multiple volumes, I would suggest attempting to backup the volume pairs databases+logs separately. For instance if C: is the system volume D: contains some databases and their logs and E: contains databases and F: contains the logs for the databases on E:, back up C; separately, D: separately and E: and F: separately (at 30 min intervals for instance). This would reduce the time the SQLWriter needs to freeze various databases.
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