Deleting a snapshot removes the snapshot from the Snapshot Manager. The snapshot files are consolidated and written to the parent snapshot disk and merge with the virtual machine base disk.
Deleting a snapshot leaves the current state of the virtual machine or any other snapshot untouched. Deleting a snapshot consolidates the changes between snapshots and previous disk states and writes to the parent disk all data from the delta disk that contains the information about the deleted snapshot. When you delete the base parent snapshot, all changes merge with the base virtual machine disk.
Deleting snapshots involves large amounts of disk reads and writes, which can reduce virtual machine performance until consolidation is complete. Consolidating snapshots removes redundant disks, which improves virtual machine performance and saves storage space. The time it takes to delete snapshots and consolidate the snapshot files depends on the volume of data that the guest operating system wrote to the virtual disks after you took the last snapshot. The required time is proportional to the amount of data the virtual machine is writing during consolidation if the virtual machine is powered on.
If disk consolidation fails when you delete a snapshot or delete all snapshots and you notice a degradation in virtual machine performance, you can view a list of virtual machines to determine if any files require consolidation, and if so, run a separate consolidation operation. For information about locating and viewing the consolidation state of multiple virtual machines and running a separate consolidation operation, see Consolidate Snapshots in the vSphere Client
Use the Delete option to remove a single parent or child snapshot from the snapshot tree. Delete writes disk changes between the snapshot and the previous delta disk state to the parent snapshot.
You can also use the Delete option to remove a corrupt snapshot and its files from an abandoned branch of the snapshot tree without merging them with the parent snapshot.
Use the Delete All option to delete all snapshots from the Snapshot Manager. Delete all consolidates and writes changes between snapshots and previous delta disk states to the base parent disk and merges them with the base virtual machine disk.
To prevent snapshot files from merging with the parent snapshot, for example in cases of failed updates or installations, first use the Go to command to restore to a previous snapshot. This action invalidates the snapshot delta disks and deletes the memory file. You can then use the Delete option to remove the snapshot and any associated files.