One of the best things about virtualization is the ability to take snapshots of virtual machines while running or while powered off. This saves countless hours spent taking backups of VM’s prior to upgrades or critical reconfigurations. If the change causes problems, simply revert back to the snapshot that you took beforehand.
It is best practice not to keep snapshots for an extended period of time, as delta (change) files related to the snapshot begin to grow and can become unstable at some point (I’ve had instances where my VMware server glitched out and ate up all storage space in my datastore by creating snapshot files). This being the case, it is best to purge unneeded snapshots as soon as you’re certain you don’t need them anymore. However, what if you have dozens or hundreds of VMs and don’t remember which ones have snapshots? You could click on each VM and see if there are any snapshots associated with it, or you can use this technique I just discovered this morning to view all snapshots in your datacenter. This is only applicable to vSphere 4.0+.
Open the vSphere Client and browse to Home –> Inventory –> Hosts and Clusters (in the top navigation pane). Select the name of your datacenter in the left-hand pane. Click the “Storage Views” tab. For View, select “Reports”. Ensure that “Show all Virtual Machines” is selected from the dropdown menu directly below the “Reports” button. There should be a column that says “Snapshot Space”. If not, right-click the title columns and select “Snapshot Space” to add that column. Then click the “Snapshot Space” column to sort it by size. You can ignore VMs that have a Snapshot Space of a few bytes or a few KBytes. Look out for ones that have a few GB of Snapshot Space. These are the VMs you need to remove snapshots from. Picture below has key areas circled.
A year after installing ESXi I found a little check box in the remediation/update manager settings that tells it to take snapshots of the guests before applying updates to the hosts. For some reason it was set to never delete them rather than the default delete them after 18 hours. I just updated it and then found your blog giving me an easy way to see how many unknown snapshots I had sitting around.