Hello,
There is a PDF that's with the Firmware documentation on the Equallogic Support side, called "OS considerations guide". This has info about setting the disk timeout value for a number of OS's. The disk timeout value needs to be set on all your VMs and physical hosts.
In ESX the Login timeout needs to be adjusted to 60 seconds.
The firmware upgrade process by default updates the flash on both controllers, then restarts the secondary to bring it up to the new level. Once that completes and re-sync's with the primary, the primary is restarted to force a failover to the upgraded secondary. Depending on model number and load on the member, this typically takes 20 to 60 seconds. With the timeouts set, servers will ride out this period without a problem. Doing upgrades in a low IO period is also suggested.
The other important consideration for making these changes is being able to handle a controller failure.
Regards,
Don