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 High Availability (2008)
 Strange mirroring issue
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chris_cs
Posting Yak Master

United Kingdom
223 Posts

Posted - 11/30/2011 :  10:33:04  Show Profile  Reply with Quote
I had an issue today where 3 mirrored databases out of 10 failed over to out DR server. I'm using High safety with automatic failover, so I'd only expect the databases to fail over if there was an issue with the server or they were manually failed over.

When I look in the error log I can see a set of entries with the message 'database mirroring is inactive for database....' for each mirrored database.

What would cause only 3 databases to failover but the others to remain ok?

I'm looking into it but thought I'd see if anyone had any ideas.

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Junior DBA learning the ropes

chris_cs
Posting Yak Master

United Kingdom
223 Posts

Posted - 12/01/2011 :  06:17:07  Show Profile  Reply with Quote
Now I've had some time to look into this the reason only three DBs failed over is because they were the only ones configured with a witness for HA! So I'm glad I've cleared that one up!

Now I'm trying to figure out what caused them to failover. From the error logs it looks as though the witness and mirror had trouble communicating with the prinicipal and once the default timeout period was exceeded (10s) the failover was initiated.

When SQL Server monitors the Quorum between the servers using a ping is this the same as a normal network ping?

At the moment I'm assuming it must have been a network issue, but a 10 second timeout would have flagged something with our infrastructure team and they cannot see any obvious issues.

How have other people gone about troubleshooting this?

----------------------------
Junior DBA learning the ropes
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