I ran into this problem a few days ago when I tried to give a vm a little more storage. I could not, it was greyed out. After looking into it I found the problem: This virtual machine was running on a snapshot. So, go to the snapshot manager and find: nothing!
Tracking the problem back: A while ago the vm needed a snapshot in order to be safe for an update. So, create snapshot, install updates. All fine. After that, the snapshot was deleted, and in the snapshot manager you did not see any snapshots.
But somehow the vms config still pointed to the delta-file instead of the original. And the delta was still growing. All in all over a 100GB, because this has been going on for quite some time now.
With vSphere 5 / ESXi5 there is a quick solution. In the virtual machines tab look for “Needs consolidation”. It is says yes, right click the vm -> snapshots -> consolidate.
But here we have ESXi 4.1 and vSphere 4.1, so no “consolidate” nor “needs consolidation”. How to fix this?
It can be done in most cases quite easily, but I needed some encouragement from others that already performed this: Create a new snapshot, and right when it is done: Delete all.
This will consolidate even the not shown snapshots and leave you with an all functioning vm.
So, for me, that did the trick. But sometimes it is not so easy. Please consider reading these links first:
Wish you the best of luck with your problem, and please read my disclaimer 😉