April 12, 2012 at 8:48 am
Environment: Principal, Mirror and Witness are all SQL 2008 R2
The Principal server hosts Database A and Database B, both of which are mirrored to the Mirror Server. Randomly Database A or Database B will failover to the Mirror server. The logs don't indicate any reason why. If the problem were related to the network or the servers themselves then both databases would failover at the same time, but they don't. One will remain on the Principal while the other fails over.
How do I get this to stop?
April 12, 2012 at 8:55 am
What is the timeout period for the mirroring for the databases, is it set to the default?
April 12, 2012 at 9:02 am
Default.
April 12, 2012 at 9:05 am
Okay. How busy or stable is your network? You may want to adjust your timeout. At a previous employer where I had setup mirroring, we set the time out to 30 seconds. Our network wasn't the most stable at times and when the timeout was set to 10 seconds we did have the occasional failover even though the servers were still operational.
April 12, 2012 at 9:10 am
But if the network were at fault, wouldn't it cause all of the mirrors to fail over? We have other principals/mirrors set up on other servers, using the same witness server and they don't have this random failover issue.
April 12, 2012 at 9:16 am
Mick Opalak (4/12/2012)
But if the network were at fault, wouldn't it cause all of the mirrors to fail over? We have other principals/mirrors set up on other servers, using the same witness server and they don't have this random failover issue.
Not necessarily. That is what was happening at my previous employer at times. One database may failover and the other wouldn't. that is why we increased the timeout period, to handle those occasional network delays that caused the errant failovers.
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