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Although VMware snapshots are an important part of backup technology, you shouldn't use them as a replacement for...
traditional backup. A snapshot is only a partial copy of a VM's disk file at a particular point in time. You can use one to restore a VM to the specific state when failures or system errors occur, but you need to monitor and consolidate VMware snapshots in case they build up and cause performance issues. Some backup tools that use VMware snapshot technology to back up VMs can leave snapshots behind. This can result in a litany of issues, including low VM performance, corrupted VMs, a loss of space on data stores as delta files grow over time and the need for disk consolidation. This makes it essential for administrators to closely monitor VMware snapshots on a regular basis.
VMware snapshots aren't complete copies of the original virtual machine disk (VMDK) files. Taking a snapshot only copies the delta disks; it does not create a complete copy of the original VMDK file. The current state of the VM is a combination of the change log in the snapshot file and the original disk file. If the base disks are deleted, the snapshot files are useless. Due to this -- and the fact that stored snapshots can rapidly build up, eating valuable storage space -- you shouldn't use snapshots over long periods of time or for the production of VMs.
Look for VMs with snapshots
There are a few ways to find out whether you have VMs with snapshots in your vSphere environment. To use the vSphere Web Client to check for VMs with snapshots, start by connecting to vCenter Server with the Web Client, and if you have several data centers configured, select either the data center or vCenter Server. Next, go to the Virtual Machines tab. Right-click the column title, and go to Show/Hide Columns…. Locate the Needs Consolidation column, then click OK to validate; this will pull up a list of VMs with snapshots.
Use RVTools to monitor VMs with snapshots
You can also check for snapshots with RVTools, a free Windows application that uses the VMware Infrastructure software development kit to display information about your VMs and ESXi hosts. As you can see in Figure C, RVTools provides information about VMs with snapshots and can export reports as CSV or XLS files.
You'll need a .NET installed on the workstation where you intend to install RVTools.
Again, it's critical that you closely monitor and consolidate VMware snapshots because most backup products generate snapshots through vSphere storage APIs. Although many backup products now double-check to see whether they've left any snapshots behind, it's still in your best interest to manually check to avoid resource waste and performance issues in your environment.
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