When i clone a VM or a template the cloning goes till around 17GB of the template or VM and then freazes for a solid minute before it continous. In this 1 minute time frame the all VMs running on that disk become unresponsive . Sometimes even dropping all connections. i am running a dell r640 here with a PERC H730P Mini (Embedded). It has 1 big virtual disk in raid 5 containing 5 samsung enterprise SAS ssds. I also noticed doing heavy IO operations inside a VM like copying 40GB files or benchmarking the disk inside a vm does not create IO delays or freazes.