You may had experienced the snapshot problem when the snapshot delta virtual disk had become huge which is more than 20GB and is not able to be truncated by removing all the snapshot. Usually the problem occur when the snapshot is no longer available from snapshot manager, but you can see the delta files available from the command prompt or physical folder that contain the Virtual machine images. I experienced the 2nd time now which I am not able to remove the snapshot on a particular virtual machine from snapshot manager and command prompt. The production virtual machine was powered off due to disk full on the specify datastore. This virtual machine contain a previous snapshot which taken 2 weeks before and yet to be truncated. The delta disk had grown up to >20 GB and fully fill up the available space within the data store.

In order to recover the virtual machine, I had to remove all the snapshots on the virtual machine, but the process hang up after 3 to 4 times I tried. You may able to perform this with command and if you are lucky enough, you should able to remove the snapshot by using command. Alternatively, you can also clone a new virtual disk image contain the delta file changes to a whole new virtual disk by using vmkfstools command. This will require quite some times for you to recover the situation mostly the business will not able to wait and it is no guarantee that the recovery will fully work as we expected.

For my case, the quickest way to recover this is to clone the entire virtual machine to a new datastore that have the disk space you require and power it up immediate after the clone. We double checked the entire virtual machines mount point and services, everything require and last file transaction is available without any issue and back to production. Now I will have my sweet time to slowly investigate the failure to remove snapshots on the virtual machines. Well, is not necessary the method I am using here is the best, but I would like to share my personal experience in the critical production time, you may wanna consider the best option to recover the production virtual machine as soon as possible.