Snaphot space question - with pictures

[RSWilson1]

Hi Folks,

This is my first post here as we're quite new to this and I want to as what may be an obvious question.

I've tried to search but as you will see from the question the specifics mean any search results do not give the information I am looking for.

Basically - I am deleting snapshots and I am aware the snapshot copies into the parent image before it deletes the snapshot itself.

As such the amount of space used actually increases before it is reduced.

Thus you need more than enough space to delete snapshots.

My question is:

Based on the two attached images, does the required space need to be in the "Used Storage" Vs the "Provisioned Storage" in the Summary View.

Or is it the "Capacity" Vs the "Space Used" in the Storage Views?

I did see my Used Storage reach the same capacity as the Provisioned Storage the last time I deleted a Snapshot and I panicked that I'd run out of space!!

I'd be grateful of anyone who can explained this to me in simple terms please.

Thank you!!

RSW

[taylorb · Accepted solution]

VM snapshots just use any free datastore space.   This free space would be the difference between the Capacity column and the Space used column.

Provisioned storage is the amount that the VM could use, and this amount doubles whenever you take a snapshot to allow for a full 100% rate of change within that snapshot.    

Mainly, you aren't going to hit major problems (like VMs halting) unless your Space Used = Datastore Capacity. 

[RSWilson1]

Thank you taylorb!

That gives me confidence.

Attached is another screenshot which (if I've understood this correctly) means my datastore [EMC01-SAS-R6-01] has 672.67 GB to play with so my VM snapshots have plenty of room in which to turn around.

Cheers!!

[taylorb]

Yes, that is correct.

[RSWilson1]

Thank you Sir - very helpfull!

This weekend I will be mostly deleting SQL Server Snapshots then (after the backup runs of course!).

[a_p_]

Just a quick comment regarding:

As such the amount of space used actually increases before it is reduced.

This actually only applies to thin provisioned virtual disks. With thick provisioned virtual disks, the consolidation itself doesn't require disk space for the merge, but only for a helper snapshot which is created if the snapshot is deleted with the VM powered on. The size of the helper snapshot depends on the virtual machine's activity while deletion is in progress.

André

[RSWilson1]

Ah right - thank you.

Just while I'm on here... any idea as to why the Storage view still shows 45.00 B of space used in the Snapshot colum AFTER the "Delete All" has been pressed?

Thanks

RSW

[a_p_]

I can't tell you for sure at the moment, but I guess this is the size of the .vmsd file, a small text file which contains the information about snapshots.

André