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Thick vs Thin Provision Snapshots?

A

Atlantian

n00b
Joined
Nov 21, 2006
Messages
55
Hey gurus, I am gettting into virtualization and have come across a question I can't seem to find the answer to.

When I create a viratual machine and have its HDD space provisioned as thick or thin, when I take snapshots of that machine does the space required to hold that snapshot allocated out a full block(say if the provision was for 100 GB) or full 100 GB, or does it simply save the "differences" from the base virtual machine and the snapshot.

Does the snapshot disk space requirement change if I have my machine setup as thick or thin?
 
No. Snaps are the same whether the base is thick or thin. Snaps simply hold the deltas (changes) between the snap and the base so they will start small and grow over time. Don't keep a VM snapshot more than 2 or 3 days.
 
Yeah, the main thing I use snaps for is before upgrading a VM. If all goes well, a day or so later, I delete it.
 
The reason I am looking into snap shots are for work I use a lot of different software packages. And it is always annoying when they upgrade, and are most of the time not compatible with each other. I am invisioning having snapshots for each version of the software, and having multple VM for each software package. That way if a client wants version 1.0 ok I can develope on there, then say another wants 2.0, I can load that snapshot and develope on there.

Or would what I am proposing be bad practice when dealing with virtual machines?
 
Theortically I believe you can have up to 32 snapshots, but VMware really states that you should only have 2-3 snaps and only for a short period of time. The reasoning behind this is that the longer the snaps are there, the bigger they can get which can cause issues if applying a large snap to the VM.

In your case you may want to create a template for the versions you need to save, deploy from the template, and take snaps prior to making changes, test, then delete the snaps but then again, you'll have a template..so the snaps probably aren't necessary unless you're looking for a quicker rollback.
 
Yeah. That's not the use case for snapshots. Just build a base template for the VM...deploy a new VM from template for each version and thin provision it.
 
Yea think of snaps as RAW Data being pumped into a VMDK file, the more changes u make the more raw data being pumped into that file, hence why it grows. When you use thin provisioning even overwriting a file in the OS can sometimes not change the Thinprovisioned size, but if you are on a snap and rewrite the same file say 2-3 times it writes it in the Delta all 2-3 times so there is a big difference between them.

using snapshots in active environments for long time == NO!
using snaps for upgrades/updates for reversion points in time == Hell yea...
using snaps for VMware View Master Images == Yes (but this is because these machines are off and updated usually when a Microsoft patch cycle is released, and we only recommend 2-3 snaps at max and no snap chaining)
 
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