Esxi how do snapshots work

Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. This site uses Akismet to reduce spam. Learn how your comment data is processed. Skip to content When I studied computer science it was not a raw science. What is a Snapshot? A snapshot file is only a change log of the original virtual disk A virtual machine uses the disk descriptor file to access the most current snapshot not the original disk. It is not a complete copy of the original disk Snapshots are combined dynamically with the original disk to form a current state of system The snapshot change logs are sometimes called delta files Think of them as chains to get the complete picture you need all the links in order.

Snapshot files will grow forever unless deleted re-integrated into original disk Using a lot of snapshots can effect performance of the virtual machine How do snapshots work?

This can be useful for any number of reasons, and quite honestly was way more useful in the early days of VMware vSphere. This point in time is very important, since it is what you need to keep in mind when it comes time to either delete your snapshot keep your changes or revert your snapshot discard your changes. Many VMware administrators like to use VMware snapshots for things like testing or keeping a clean copy of a VM before changes are made. The key thing is not taking the snapshot itself, but what you do with your snapshot when you are done with it.

If you see issues in your environment from VMware snapshots, 9 times out of 10 they will be because a snapshot was left open in perpetuity. After you take the VMware snapshot, all other changes that are made to a VM are stored to a delta file.

This delta file of course grows and grows as the snapshot is left open, and changes are made. Every write from your snapshot forward ends up in the delta file. Think of a VM that makes lots of transactions without intervention, like a database.

All of these changes are written to this delta file. This delta file, more importantly the size of this delta file is very important when it comes to VMware snapshots. Beyond the delta file, there are additional files created when taking a VMware snapshot.

If your change goes great, fantastic! However, you now need to delete that snapshot, or keep your changes. This is where you will see issues with VMware snapshot performance, not necessarily taking the snapshot or having it open, but when it comes time to delete the snapshot.

Once, I had a major storage performance issue in an environment when I was a VMware administrator, and we discovered it because snapshots were literally taking DAYS to delete. The other drawback of VMware snapshots is that they are easy to forget about, which can once again lead to the first drawback. The most useful script we had in our VMware environment was one that e-mailed us daily with a list of open snapshots in our environment so we could keep track of them before we encountered issues.

Some of the things we talked about sound pretty horrible, especially when it comes to the performance when deleting a VMware snapshot. There are many good reasons to use a VMware snapshot, as much as they can be come a problem if they are ignored. Besides having a clean copy of your VM ready to go if something goes wrong with a patch, upgrade, or test, there is one other major benefit of VMware snapshots.

This is a nice way of saying that if something goes terribly wrong with your VM, things will start right up without issue should you need revert to a snapshot. It requires VMware Tools to be installed in the virtual machine. Virtual environment Virtual machine VMware. VMware Security Best Practices. Vladan Seget July 2, The Basics of Virtualization Security.

Vladan Seget October 8, Krishna Kumar October 28, Hyper-V Security in Windows Server Ryan Brooks June 10, Featured tags. We care about security of your data. Privacy Policy. Great things come to those who sign up. Get expert advice on enhancing security, data governance and IT operations. Get expert advice on enhancing security, data management and IT operations, right in your inbox. Thank you for subscription.