VirtualBox Fail - inaccessible ?

[jvsrvcs]

I launched my virtual box manager this morning and saw a VM unaccessible. I really need the VM, it was a key one.

I get the following message:

How do I fix this? How do I prevent this from happening? What happened?


---
The selected virtual machine is inaccessible. Please inspect the error message show below
and press the Refresh button if you want to repeat the accessibility check:

A differencing image of snapshot {2f12bf4b-.....} could not be found. Could not find an open hard disk

Result Code: E_FAIL (0x800004005)
Component: SnapshotMachine
Interface: IMachine {5eaa9319-...}

[Perryg]

What happened between the time it worked and now?
Where are the guests files stored? Local, remote, Etc.

[mpack]

I really need the VM, it was a key one.

Just a suggestion, but perhaps if the data is that important you should in future avoid snapshots - and make backups.

This one sounds like the classic case of deleted snapshot file in the host OS, or snapshot deletion gone wrong using when the GUI. I think we'll need to see the .vbox file for this VM (as a zipped attachment please), and a list of the contents (or picture) of the VM folder, ditto the VM "Snapshots" subfolder. Also the VirtualBox version number.

[jvsrvcs]

I did not do anything to the box between the time of working and failure.

The recommendation to avoid snapshots is useless. VirtualBox is useless to me unless I can make heavy use of snapshots. I am using it for QA and being able to restore a specific state or starting point is essential.

[jvsrvcs]

I really need the VM, it was a key one.

Just a suggestion, but perhaps if the data is that important you should in future avoid snapshots - and make backups.

This one sounds like the classic case of deleted snapshot file in the host OS, or snapshot deletion gone wrong using when the GUI. I think we'll need to see the .vbox file for this VM (as a zipped attachment please), and a list of the contents (or picture) of the VM folder, ditto the VM "Snapshots" subfolder. Also the VirtualBox version number.

The .vbox file is referencing a snapshot that does not exist. I am not sure what happened. I ran out of disk space at one point. Maybe some boundary points of VirtualBox have not been tested such that when there is no disk space left, files are deleted.

At any rate, I am close to or out of disk space, did not have this VM backed up and have lost some serious work here.

[Perryg]

VirtualBox allows you to set the size of the virtual drive but that is extended on each snapshot you take. I honestly don't know of any product other than the host OS that can watch and tell you that you are close to running out of disk space. Did you see any warning from the host about getting low on space?
As for using snapshots they do have their place. Saying that you must be sure to back these up and the control files regularly because stuff happens.

Where in the snapshot chain is the one referenced that is missing? Is it the current state snapshot?

[mpack]

VirtualBox is useless to me unless I can make heavy use of snapshots. I am using it for QA and being able to restore a specific state or starting point is essential.

You can do that with proper backups, without wasting host disk space and without rendering the VM liable to control file corruption problems like you have suffered. If you had already been using real backups then you simply would not have had any of the above problems - but if we pretend that you did then you still would have recovered from it easily. The truth is that it's backups that are essential, not snapshots.