Problem with failover BackEnd Lync 2010

Hi,

We use a lync 2010 entreprise edition. We have a cluster of 2 Back-END.

But when one of them crashes, sometimes, we lose the connectivity to the adress book for 10 minutes on lync client. The sql services is ok after 5 seconds, but not the client.

We need to restart the client (or to delete cache files) to be more reactive.

Is-it normal? I don't find anything on it?

Thanks