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SQL unavailable during backup

Post by kangarolf »

Hi all,

VEEM Backup and Replication 9.5

I use the powershell extensions to schedule a full backup at 2:30am every morning.

Previously there was no issue but for the last 2 weeks I get connection unavailable errors for MSSQL on the guest OS when it is backing up at 2:30.

On the guest OS I get warning entries in the system log for a suprise removal of disk 1 and then warnings about the signature of disk 0 being equal to disk 1.

The errors returned from the applications (.net) trying to access the MSSQL server are either that the 'server was not found' or that the 'semaphore period as expired'.

Is this normal..? Should the MSSQL server fail to respond when the OS is being backed up by VEEM?

Thanks for any advice

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Re: SQL unavailable during backup

Post by Gostev » 1 person likes this post

Hello, this may indeed happen during backup to poorly written applications that expect 100% SQL Server availability and doesn't feature retries. Remember that application-consistent backup requires quiescing SQL server with SQL VSS Writer, which in turn pauses databases for a brief moment, flushes RAM caches to disk and creates a consistent VSS snapshot.

The reasons you did not experience this issue before may include having fewer or smaller databases and SQL Server needing less time to quiesce itself as the result, staying under the application's timeout, or because the application was not as active during the backup window before, or due to SQL server disks fragmentation causing performance issues, or for many other reasons. No environment is completely static...


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