vSphere Snapshot question

Is there any kind of standard method for determining how much space you should leave on a LUN for snapshots of VM's?
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CptnTripsAsked:
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jhyieslaCommented:
If you're using snapshots as they are intended to be used not really, except you may need as much free space as the snap used in order to roll in into the VMDK file. See below for an explanation of snapshots.

A snap shot is a way to preserve a point in time when the VM was running OK before making changes. A snapshot is NOT a way to get a static copy of a VM before making changes.  When you take a snapshot of a VM what happens is that a delta file gets created and the original VMDK file gets converted to a Read-Only file.  There is an active link between the original VMDK file and the new delta file.  Anything that gets written to the VM actually gets written to the delta file.   The correct way to use a snapshot is when you want to make some change to a VM like adding a new app or a patch; something that might damage the guest OS. After you apply the patch or make the change and it’s stable, you should really go into snapshot manager and delete the snapshot which will commit the changes to the original VM, delete the snap, and make the VMDK file RW. The official stance is that you really shouldn’t have more than one snap at a time and that you should not leave them out there for long periods of time. Adding more snaps and leaving them there a long time degrades the performance of the VM.  If the patch or whatever goes badly or for some reason you need to get back to the original unmodified VM, that’s possible as well.  
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CptnTripsAuthor Commented:
Thanks for the information. I think I understand the nature of snapshots as only being temporary and that they should not be used arbitrarily. I also understand that they are just delta changes but there has to be some kind of formula to determine space.

For instance, I have a LUN that is 2TB. That LUN is carved up for 8 VM's. I would assume that there is some way to determine how much space I need to leave on that LUN for snapshots. I don't have enough on there now for 3 to have snapshots at the same time.
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CptnTripsAuthor Commented:
The section on "Virtual Machines with Snapshots" is getting pretty close.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003755
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jhyieslaCommented:
The other expert's link should help.  I think that the bottom line is that it really depends. If you create a snap on a machine that has very little written to it, the snap will be very small; and vice versa. The only think that I've heard is that you will probably need as much space as the snap is taking up to roll it into the original VMDK. So, my understanding is that if your snap grows to 1 GB, you would potentially need another GB in order to roll it.
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CptnTripsAuthor Commented:
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