In Database Mirroring there is a Timeout setting that specifies the time in seconds a server waits to receive a ping message from another server in the mirroring session. This timeout setting is by default 10 seconds. You can set this higher but not lower than 5 seconds. If you have problems with network latency or if the servers involved in the mirroring setup are on different locations with great distance between it might be a good idea to adjust the timeout setting in order to avoid false failures.
For example, to set timeout to 15 seconds run the following on the principal server: ALTER DATABASE XXXX SET PARTNER TIMEOUT 15 Setting the timeout value too high will result in automatic failover taking longer time and setting it too low may result in unnecessary failovers. As always, it depends….