The Release notes for 4.x firmware or the OS Consideration guide that's with 5.0.x firmware on the Equallogic website has information about setting the correct disk timeouts for Windows and Linux.   ESX itself is fine, but the individual VMs might not be.  The default disk timeout value is 30 seconds.  That should be extended to 60.   More recent versions of VMware tools does this for Windows automatically.   This is important not only for a manual fail over like you are doing but also in case there's a real HW problem one day the the controller failover.   Some applications are more sensitive.  Especially SQL and Exchange.  They may send alerts during the failover.    There are a number of factors that influence failover time.   Load on the array at the time, number of iSCSI connections, etc..   If you can do so during a quieter IO period, that would be best.   Regards,   -don 
What precautions do I need to take before initiating a controller failover. It had a bad drive replaced with a new one but GUI still has red X mark on it. Dell tech says a failover will fix it but it has bunch of production VMs running on it. Will a controller failover with live VMs create any issue ? what do you recommend ?Thank you. 
Dell EqualLogic PS5000E controller failover