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At that point, all of the VM's write operations are directed to the newly created differencing disk.

When you create a snapshot, Hyper-V creates a special-purpose virtual hard disk called a differencing disk. When you create a Hyper-V snapshot, what you are really creating is a differencing disk.Īs I'm sure you probably know, Hyper-V VMs generally have one or more virtual hard disks associated with them. Conversely, when you create a Hyper-V snapshot, Hyper-V is not making a copy of the VM or its data. When you create a backup, you are creating a copy of whatever it is that you're backing up. The reason I say this is because Hyper-V snapshots work in a manner that is completely different from backups. Whereas it might take hours to restore a VM from backup (depending on the VM size and the backup infrastructure being used), a snapshot can be restored in a matter of seconds.Įven so, Hyper-V snapshots exist primarily as a convenience, not as a backup replacement. That being the case, I wanted to take a moment to talk about one particular term that can be especially problematic: snapshots.įrom the time that Microsoft introduced Hyper-V way back in 2008, it has been well-established that Hyper-V snapshots are not a viable substitute for traditional backups.įor those who might not be familiar with Hyper-V snapshots, they are a tool that can be used to revert a virtual machine (VM) to a previous state, but without the hassles of restoring a backup. Not only have backup methods and technologies changed, but so has some of the terminology. Among many other things, the cloud has had a huge impact on the way that we perform backups and disaster recovery operations. The public cloud is easily one of the most transformative IT technologies of all time.