Environment Details: Server 2012 datacenter Hyper-V Cluster with 2 nodes, identical HP DL380 G8's.
a server VM was intitially Created as a non clustered VM. It had a data disk attached as a SCSI device. i deleted the initial VM, then created a new one as a clustered VM and when i try to reattach the data disk it gives the error you see attached.. no errors attaching the OS disk, just the Data Disk.
I've tried removing the VM files and locks manually with no luck, i've also tried attaching the drive to another VM and it gives an error saying its already attached to whatever VM you try to attach it to... this would imply that its something to do with the disk itself and not the VM? i've also tried renaming the offending data disk to see if i could trick it, but no luck... I converted the volume that the disk is residing on to a Cluster Shared Volume also but i'm unfamiliar with exactly what happens when this is done and whether it may have contributed to the issue as i also did it to the volumes containing the OS disks.
It doesn't always happen so it seems to be a bug with Hyper-v and clustering/CSV's?, i've done the same with a file server and only a few of the disks have this error.... which is better than all of them but still sucks...
Hope someone can help! :)