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.

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