I'm testing a 2 node windows failover cluster with mirroring in high safety mode and automatic failover. My mirror is a standalone server as is the witness. All instances are 2008 R2 RTM Enterprise Edition (64-bit) (this is a test, the witness will be Express in prod)
Because I'd like to prevent failover to the mirror when I failover one cluster node to the other (or in the case we just lose a node), I've upped the partner timeout value. My cluster fails over fairly quickly, somewhere between 25 and 30 seconds. But, even when I set the value of the timeout to 59 seconds, the mirrored DB still fails over to the mirror server, and rather quickly.
Generally, I'm testing by simply moving the SQL resource from one node to the other in the cluster manager but I did try it by rebooting the active node as well. The same is true when I failback. I can shutdown the SQL Service on my mirror server (which is now the principle) and by querying sys.database_mirroring, I see the mirror (former principal) change state and description in very short order.
So, what am I doing wrong or assuming about how the timeout works?
Best Answer
I'd suggest that the clean shutdown of the principal is causing it.
From Automatic Failover
One may assume that the principal says "I'm DISCONNECTED" on clean shutdown
To test this correctly, remove the network cables (or power leads) from the node hosting the principal to simulate/invoke a "real" server failure
I assume that the mirror is actually remote and not on the same cluster...