We have huge storage with all kinds of VDIs mcs, pvs, standalone vms etc on our vcenter. We have removed VDIs in bulk and added new VDIs in citrix. That created lot of I/O on the storage and it increased to 100% usage  all of sudden. PVS machines power on, load boot strap and stop. MCS machines are powered on but doesnt respond in vmware and citrix.

We have identified VDIs thats causing high resource utilization on each host in our VDI cluster and started rebooting those machines. This brought down stress on storage, and issue resolved.