We have a Dell Equallogic iSCSI SAN that we use for Storage. Connected with 4 - 1gbps, sorry, I'm not sure on the policy.
We don't use snapshots for backups. We have only created snapshots before applying a service pack or upgrade to a guest, so we had a rollback. But we also do not have a backup of the actual VMDK's if something were to happen. (we backup the guest OS thru Backup Exec, old school... trying to get the budget funding to change that.
My fear is - the only other time I have deleted an old snapshot was a snapshot on the exchange mail server. At the end of the delete the process actually made the guest stop responding and all users lost access to our email system for approx 20 mins. It was an unexpected and unplanned outage. My fear is by doing this process to some of my other servers - the same thing will happen. Losing access to our patient record system (we are 24x7 healthcare) would not be a good thing. We have to plan outages, so I need to figure out what to expect.