I am seeing an odd issue with Hyper-V vms on pass-thru disks. Say an event occurs on the storage array that causes the disks on the Hyper-V server go offline momentarily. They can be brought back online afterwards. Hyper-V then loses the handle on the disk. There are four broad categories of symptoms that then occur:

1.  Very broadly speaking, if the disk contains server-specific information such as a paging file, then the server behaves erratically when it goes offline.
2. If the disk in question goes offline and it contains the vm definition files (.bin, .vsv), then the vm disappears from the Hyper-V console.
3.  If the disk goes offline and it contains vm disks (.vhd), then the vm in question crashes.
4. If the disk is directly mapped to a vm as a host resource, then the vm is shutdown. Sometimes the state is saved. The settings show that the physical disk cannot be found. The vm’s saved state has to be deleted and then the physical disks reselected in the vm settings dialog.

I am still troubleshooting. More details to follow.

Posted October 16, 2008 by Wolf Goerlich