If the host server is busy backing up (all vms show "backing up..." as status) and I copy a large amount of data to one of the VM's (a gb or more), all the VM's lock up.
while the vms are locked up I end the "Block level backup service" task and it takes a few minutes before the vm statuses stop showing "backing up..." and then the vm's start behaving normally again.
there are only 2 vm's running and another that is not running. all vm's have server 2012 standard. the running VM's are replicating also.
The disk queue for both the host's c drive and the drive where the vm's vhd's are located are not very high.
This happens when copying files to vm's with either fixed or dynamically expanding VHD's.