Hi Bernd,

to me it looks like a problem with the interaction with the hypervisor. I haven't toyed with HyperV yet, so have no practical experience with it. But those numbers don't look very impressive to me, except for "the disk is 100% busy"

If the LUNs aren't as busy on the host system, too, then maybe some optimization regarding that driver interface could improve the situation, but that's beyond what I can be of help with. Do you have a vendor for the HyperV system you could ask for details on the hypervisor side of things?