Matthijs Haverink writes on his blog at his site virtualfuture.info about an incident at a customer site.
Last month I was on-site at one of my customers and experienced a major problem on the vSphere environment. We suddenly experienced about 150 virtual servers running on 16 hosts in 2 clusters (on the same SAN) going in jabber-mode. They froze, which made them unavailable for pings and other traffic. The freeze moment varied from 1 to 30 seconds. After that the VM’s went back on-line again. This seemed to happen in groups of about 10 to 30 VM’s.
It was found out that this problem was caused by a deletion of a LUN without performing a rescan of the storage.
More info on the links below.