VMware snapshots are useful because they restore VMs to a specific state. But snapshots can also cause performance problems.

Although VMware snapshots are an important part of backup technology, snapshots should not be considered a replacement for traditional backups. A snapshot is only a partial copy of the virtual machine (VM) file stored on disk at a specific time.

You can use a copy to restore a VM to its specific state when a failure or system failure occurs. But you need to monitor and consolidate VMware snapshots in case they cause performance problems.

Some backup tools that use VMware Snapshot technology to back up VMs may leave snapshots. This can lead to a variety of problems, including low VM performance, corrupted VMs, or a loss of storage space as delta files grow over time and the need for disk consolidation increases. For administrators, it is therefore essential to closely monitor VMware snapshots on a regular basis.

VMware snapshots are not full copies of the original Virtual Machine Disk(VMDK) files. For a snapshot, only the delta files are copied. A complete copy of the original VMDK file will not be created.

The current state of the VM is a combination of the changelog in the snapshot file and the original VMDK file. If the base disks are deleted, the snapshot files are useless. Because of this and the fact that stored snapshots can be set up quickly and take up valuable storage space, you should not use snapshots for extended periods of time or for the production of VMs.

Search for VMs with snapshots

There are several ways to find out if you have VMs with snapshots in your vSphere environment.

To use the vSphere Web Client to scan VMs with snapshots, first connect to vCenter Server through the Web Client. If you have multiple data centers configured, select either the data center or vCenter Server. Next, select the Virtual Machines tab. Right-click the column title and select Show / Hide Columns. Locate the Needs Consolidation column, and then click OK to bring up the list of VMs with snapshots.

RVTools monitors VMs with snapshots

Also with RVTools snapshots can be searched. RVTools is a free Windows application that uses the VMware Infrastructure Software Development Kit(SDK) to display information about your VMs and ESXi hosts. As you can see in Figure 3, RVTools provides information about VMs with snapshots and can export reports as CSV or XLS files.

 

If you want to install RVTools, you must have .NET installed on the workstation where you want to set up RVTools.

Conclusion

It is important that you closely monitor and consolidate VMware snapshots because most backup products generate snapshots through vSphere APIs. Although many backup products now double-check their ability to leave snapshots, it’s still in your interest to manually check them to avoid wasting resources and performance issues in your environment.