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Mar 05, 2014 at 02:28 AM

SQL Server AlwaysOn Failover threshold and Lease Timeout


Hi experts,

I found each time when I were building/restoring another log shipping(standby) server. It would cause ERR [RES] SQL Server Availability Group: [hadrag] Failure detected, diagnostics heartbeat is lost(in cluster log) and A connection timeout has occurred on a previously established connection to availability replica 'DL980-4' with id(in errorlog). I google and find a document ( ) indicated that “This may be a performance issue”. I run restore database and AlwaysOn synchronizing on the same 10GbE link at the same time.

Should I increase

leaseTimeout from 20000 to 100000 and

HealthCheckTimeout from 30000 to 300000?

Does it work to prevent unnecessary failover.


Please refer to

( )


10-18-2013 3:19 AM


Hi Denzil

we seem to see lease expires very frequently when the server is under very high cpu pressure .. our failure condition level is 1

is it possible to prevent this situation . the problem is when lease expires,all the current connections seem to be dropped . wondering if there is a way to prevent this ..

Also is it possible to affitinize the always on health check process to a particular core

Thanks for your help!