KB1002836 "A snapshot removal can stop a virtual machine for long time (1002836)" suggests that stun time for ESXi5.5 will depend on how long it takes to process the last -delta.vmdk file.
We have seen stun times for one of our Exchange servers to exceed an hour. This stun seems to be related to Veeam snapshot processing. Is over an hour really the best that we can do?
Here are two entries of interest from vmware.log:
2016-10-16T04:30:27.886Z| vcpu-0| I120: Checkpoint_Unstun: vm stopped for 3862324390 us
2016-10-18T13:09:27.648Z| vcpu-0| I120: Checkpoint_Unstun: vm stopped for 3830417246 us
Note: the snapshot was not removed but had to be manually removed later - manual removal did not result in any extend stun.
The back end is a FAS3250 in 7-Mode.