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Mirroring restore rate very low (< 5 MB/sec) - database mirror stuck in "synchronizing" state for...


Mirroring restore rate very low (< 5 MB/sec) - database mirror stuck in "synchronizing" state for several hrs

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Marios Philippopoulos
Marios Philippopoulos
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A production mirroring session started synchronizing this morning and at first the restore rate on the mirror server was at about 30 MB /sec.
Suddenly it dropped to < 5 MB /sec and has stayed like this for most of the day.

As a result, the mirror has been in "synchronizing" status for most of the day, and we are unable to create snapshots for reporting users.

What could be the cause of such a low restore rate?
What should I be looking for?

Any links/suggestions would be most welcome.

__________________________________________________________________________________
SQL Server 2016 Columnstore Index Enhancements - System Views for Disk-Based Tables
Persisting SQL Server Index-Usage Statistics with MERGE
Turbocharge Your Database Maintenance With Service Broker: Part 2
David Webb-CDS
David Webb-CDS
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Just some random thoughts:

Check the disks for contention
Check to see if anything else is running on the box and consuming inordinate CPU and/or memory
Make sure your anti-virus software isn't on and attempting to scan your database files
check the sql server for blocked processes
Depending on how far the data is travelling, you might have to have your network folks take a look at the traffic between source and mirror



And then again, I might be wrong ...
David Webb
ksrikanth77
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I think the above all is sufficient to get the culprit
but mostly It would be Network Bandwidth

Thanks
S.R.Kundur
Marios Philippopoulos
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Thanks both for your suggestions.

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SQL Server 2016 Columnstore Index Enhancements - System Views for Disk-Based Tables
Persisting SQL Server Index-Usage Statistics with MERGE
Turbocharge Your Database Maintenance With Service Broker: Part 2
Robert Davis
Robert Davis
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There is also a bug related to this (though I don't know if a KB has been published Try stopping and starting the mirroring queues to see if it resolves the problem. If not, continue investigating and consider opening a case with PSS.



My blog: SQL Soldier
Twitter: @SQLSoldier
My book: Pro SQL Server 2008 Mirroring
Microsoft Certified Master, SQL Server MVP
Database Engineer at BlueMountain Capital Management
Marios Philippopoulos
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Robert Davis (7/17/2012)
There is also a bug related to this (though I don't know if a KB has been published Try stopping and starting the mirroring queues to see if it resolves the problem. If not, continue investigating and consider opening a case with PSS.


Thank you for the suggestion.
Do you mean suspend and resume the mirroring session?
I will try that next time this happens.

__________________________________________________________________________________
SQL Server 2016 Columnstore Index Enhancements - System Views for Disk-Based Tables
Persisting SQL Server Index-Usage Statistics with MERGE
Turbocharge Your Database Maintenance With Service Broker: Part 2
Robert Davis
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No I meant stop/start the mirroring endpoints. Use an Alter Endpoint caommand and do it on both partners.



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Database Engineer at BlueMountain Capital Management
Marios Philippopoulos
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Robert Davis (7/18/2012)
No I meant stop/start the mirroring endpoints. Use an Alter Endpoint caommand and do it on both partners.


Thanks for clarifying, now I know what you mean; will try that.

__________________________________________________________________________________
SQL Server 2016 Columnstore Index Enhancements - System Views for Disk-Based Tables
Persisting SQL Server Index-Usage Statistics with MERGE
Turbocharge Your Database Maintenance With Service Broker: Part 2
Marios Philippopoulos
Marios Philippopoulos
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Could the slow restore rate be caused by high file fragmentation on the mirror server?
Perhaps we are due for a file defrag outage.

__________________________________________________________________________________
SQL Server 2016 Columnstore Index Enhancements - System Views for Disk-Based Tables
Persisting SQL Server Index-Usage Statistics with MERGE
Turbocharge Your Database Maintenance With Service Broker: Part 2
Robert Davis
Robert Davis
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Marios Philippopoulos (7/21/2012)
Could the slow restore rate be caused by high file fragmentation on the mirror server?
Perhaps we are due for a file defrag outage.


No file level fragmentation would cause a slow degradation of performance, not a sudden one.



My blog: SQL Soldier
Twitter: @SQLSoldier
My book: Pro SQL Server 2008 Mirroring
Microsoft Certified Master, SQL Server MVP
Database Engineer at BlueMountain Capital Management
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