Comment 15 for bug 959637

FWIW: ZFS on Linux also apparently does not support Direct I/O, because I had the same problem with inability to start VMs with disks set to cache=none. I thought it was a bug in KVM causing the option to completely fail, until finding this bug while looking to file my own bug - but when I tested moving my .qcow2 file to an ext4 partition, sure enough, cache=none worked fine then.

I propose a more informative error dialog should be thrown when this occurs - "filesystem [path] does not support Direct I/O, cache=none not supported" would be a tremendous improvement over the generic "failed to connect to monitor" that's thrown now.