Take a snapshot and attached disks are detached

[Mark Cranness]

In some circumstances (VMs with shared attachments), taking a snapshot causes attached drives to be un-attached / removed.

Repro:

• Two new machines (A, B) with no attachments, 5 virtual disks: A1, A3, B1, B3, SHARED.
• Attach to A the following disks (in this order): A1, shared, A3 and add a CD/DVD controller and drive and a floppy controller and drive.
• Attach to B the following disks, B1, shared, B3 and add a CD/DVD controller and drive and floppy controller and drive.
• Take a snapshot on A. Not that now only A1 is attached, and the other disks AND the CD/DVD drive and floppy drive have been removed.
• Attempt to-reattach A3 to VM A. Note that A3 is shown with the blue star icon, indicating that a differencing disk is attached somewhere (so VB thinks).
• Virtual Media Manager > Observe that A3 does NOT have a differencing disk.
• Restore Snapshot on A and Delete Snapshot on A
• (STRANGE!) Repeat add drives to A and snapshot and this time the snapshot does not remove the attachments!
• Delete Snapshot, and observe: "Failed to delete the Snapshot 1 of the virtual machine A. Medium 'C:\...Shared.VDI' is locked for writing by another task."
• Close VirtualBox, wait for VBoxSVC.exe to stop, Delete snapshot 1 works. Re-add snapshot, followed by Delete snapshot gives error above again.

[Mark Cranness]

Another person has reported the same problem:

​http://forums.virtualbox.org/viewtopic.php?p=150687#p150687

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.