What it means to "commit a snapshot"

[sfortuna74]

Hi guys -

I am attempting to explain in lay terms what it means to "commit a snapshot"... Could someone help me out with some straightforward verbage? I know it's a simple question, but I really appreciate it.

Thanks,

Steve

[rriva · Accepted solution]

In a real simple way :

When you create a snapshot you put the vmdk disk in readonly mode and all the changes will written in a delta file.

Then you have two options :

1) Commit the snapshot it means that the system will write all the changes on the delta file on the original vmdk disk and THEN delete the delta, so you don't lose the operations after the snapshot. The option you must choose will be "Delete the Snapshot"

2) The other options will be "Revert to Snapshot" and in this case the system will delete the delta file, without write the last operations to the original vmdk file and put the vmdk file in readwrite mode again.

Hope to be clear

Bye

Riccardo Riva

VCP,RHCE,FCNSA

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[azn2kew]

"Commit a snapshot" is basically update to the delta and remove the old snapshots and its is best practices to remove snapshot before doing VMotion. When you have old snapshots in place for months and it keeps growing, it really hard to remove it (meaning commit) so there are different scenario to use for troubleshooing. Are you experiencing deleting snapshot problem right now?

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Regards,

Stefan Nguyen

VMware vExpert 2009

iGeek Systems Inc.

VMware, Citrix, Microsoft Consultant

[VMmatty]

I think one of the easiest ways to explain it is to simply say that committing a snapshot is like saving your changes. All changes you made since you took the snapshot are 'saved' back into the server (VMDK file). It's not all that different than, say, an Exchange server that is writing logs and those logs are commited to the database during a backup. Reverting a snapshot is simply undoing all of your changes and going back to the beginning when you took the snap.

That is a good way to think about it in lay terms without worrying about delta files or VMDK files or things like that.

[K-MaC]

Let's make an example that has nothing to do with computers

You have a 3ring binder(Main/Base VMDK) of your classnotes which you store all of your notes inside of. After taking notes on loose paper for a day(snapshot) you decide to put your loose paper inside of your binder(commit snapshot). Now as others have pointed out, if you continue writing notes on loose paper for a long time and dont put them inside of your binder then you will quickly run into a disorganized mess and it will be difficult to put all your loose notes inside your binder in any discernable order.

I'm assuming that you are trying to explain the process to someone who is not familiar with computers. If this is not the case sorry for the over simplified explanation.

Cheers

Kevin