ESXi 4.1 Snapshot commit operations takes randomly a long time

Hi guys,

i have a weird issue here. Scenario:

ESXi 4.1 build 800380.

Windows 2003 R2 Server

NFS datastores on a RAID10 EMC VNXe array

I take a Veeam backup of a DB machine every 30 minutes. Once a day, completely randomly, the machine get stuck removing the snapshot, it takes up to an hour. Normally the snapshot removal operation takes less than 30 seconds. When i have the problem i have high %CSTP and the CPU on the VM is very very high. This is random, and no changes are made during the snapshot, CBT usually transfer less than 100MB.

IOPS cant be as the entire virtual machine (snapshot as well) resides on superfast RAID10 SAS volume. Network is very low as well.

Ideas?

thanks