If you use VMware snapshots, there are a number of considerations that go along with them. The largest consideration is to understand that they will cause increased disk usage and, if forgotten about and left open, they will degrade performance over time. This can be compounded as an individual virtual machine can have multiple snapshots taken for different points in time.
That being said, snapshots are a great technology for VMware virtual machines (as well as other hypervisor technologies). In fact, many technologies leverage virtual machine snapshots for things like backups.
It is important however, to ensure that snapshot usage stays in check. We also have to ensure that nothing goes wrong with a snapshot being taken or removed. If there is any type of anomaly in the process, VMware has a remediation step for the virtual machine called snapshot consolidation. In this technique, any snapshots that are disconnected from the virtual machine, or are otherwise in play on the disk for the virtual machine, are corrected. This will enable future snapshots to be taken and ensure that disk usage as well as snapshot features are correct.Within the vSphere Client, you can add a column to the view to display if the virtual machine needs to have consolidation performed. Figure A below shows this option added to the list of virtual machines in a cluster.
With this selection displayed, system administrators can easily have a quick view of the virtual machines and identify if a virtual machine needs consolidation.
If one or more virtual machines do require consolidation, you can do it right away. Keep in mind that there will be an increased amount of storage I/O to correct the snapshots on the virtual machine. This may also take a long time depending on a number of factors. More information on the snapshot consolidation process for vSphere 5 can be found at VMware KB 2003638.
What tips and tricks do you employ for the snapshot consolidation process? Share your experiences below.
Rick Vanover is a software strategy specialist for Veeam Software, based in Columbus, Ohio. Rick has years of IT experience and focuses on virtualization, Windows-based server administration, and system hardware.