Snapshot is very useful when you update software or perform any modifications to the operating system. It gives you the chance to recover VM in the event of any failures. However, too many snapshots take too much storage on the host. To keep the data while deleting the snapshots, you need to merge Hyper-V snapshots to the virtual disk. See how to do it step by step in this passage.
Updated by Nick Zhao on 2024/01/24
Server virtualization technology increases the work efficiency of IT environment and Hyper-V is one of the most chosen virtualization solutions.
It is easy to create and use virtual machine in Hyper-V virtual environment. In the daily work of IT administrator, one of the tasks is to make sure that virtual machine is always available. With such a convenient virtualization platform, IT administrator could use snapshot as Hyper-V disaster recovery tool to save the state of virtual machine in the short term.
The following sections would let you know how Hyper-V snapshot works and how to merge snapshots of Hyper-V virtual machines.
To make sure you can always go back to the last step in the event of failure, you must want something like “time machine”. In fact, snapshot is the feature that works like time machine.
Hyper-V snapshot is used to save the state (powered-on, powered-off, or suspended) and data (disks, memory, virtual network interface card, etc.) of VM, like taking a picture. Although snapshot allows you revert virtual machine to the previous state, it cannot replace backup. There is a post introducing the differences between snapshot and backup.
Snapshot saves only the status of VM. In other words, it saves only the progress of VM data. If you have taken a picture of a person, you could take another picture at the same location with the same person, expression, gesture, etc. This is similar to how snapshot works. If you can not find the original elements, how could you put them into the original places? That’s why VM backup is important.
Like physical machine has its HDD, virtual machine also has its virtual disk to store data. In Hyper-V virtual environment, it exists as the .vhds format file (formally .vhd), which stores VM data like HDD. When you create a snapshot of a Hyper-V VM, a file of .avhdx (formally .avhd) format would be generated to save the state of VM.
Snapshot feature in Hyper-V virtual environment is also called checkpoint. In Windows 10 Hyper-V, there are 2 kinds of checkpoints: Standard Checkpoints, which take a snapshot to save VM state, and Production Checkpoints, which create a data-consistent backup of the virtual machine. If you have problem checkpointing Hyper-V VM, refer to this post how to fix checkpoint operation failed.
Snapshot is very helpful for avoiding failures during software updates and installations, system updates, and other progresses but too much snapshots might leave little storage for VM and cause performance issues, so you need to merge the snapshots to get more storage.
If you need the data in the snapshot files but also want to get more storage, you can use Hyper-V Manager to merge the snapshots to the parent disk to delete the snapshot files.
The multiple snapshots have formed a snapshot chain and they need to be merged in proper order. The first step is to merge the latest snapshot to its parent disk, the last snapshot of the latest snapshot, so you should manually check the order of the snapshots by the following steps:
Open Hyper-V Manager > select the VM > click Inspect Disk in Action tab > select one .avhdx file > click Open > you could get the name of its parent disk in Virtual Hard Disk Properties
Repeat the steps to get the right order of VM snapshots, then shutdown the machine and start to merge snapshots:
Open Hyper-V Manager > select the VM > click Edit Disk in Action tab > you would see the Edit Virtual Hard Disk Wizard and click Next > click Browse when asked where is the virtual hard disk file located > select the latest .avhdx file > click Open > click Next > select Merge > click Next > select To the parent virtual hard disk > click Next
Repeat the steps until all the snapshots (.avhdx files) are merged into the parent disk (.vhdx file).
After merging all the snapshots, you could export Hyper-V VM to store the entire VM.
Snapshot could only help you revert virtual machine to the previous state when the parent disk and the snapshot file are complete. If you lost the files, you lost data and can’t recover it. The effective way to protect VM data is making VM backup with Vinchin Backup & Recovery.
With Vinchin Backup & Recovery, you could quickly build your backup system for Hyper-V virtual environment and easily make VM backup.
Agentless Backup: Deploying agents on every VM has been the past. Use Vinchin Backup & Recovery to directly interact with the hypervisor layer and quickly select and backup all the VMs on the Hyper-V host.
Speedkit: Speed up the incremental backup to quickly save your recovery point.
Deduplication and Compression: Duplicate data is useless but still takes storage. Vinchin Backup & Recovery would help exclude it and save 50% storage.
Granular Recovery: Sometimes it is certain files in backup that are needed. You could perform file-level recovery with Vinchin Backup & Recovery.
There are more advanced features of Vinchin Backup & Recovery waiting for you. Try it with a 60-day full-featured free trial.
Snapshot is useful for reverting virtual machine to the previous state after failures of software update, system update, or other processes. It is also called checkpoint in Hyper-V virtual environment.
Too many snapshots might take much storage of the host. Merging Hyper-V snapshots to the virtual disk might mitigate the storage issue. Backup is better than snapshot in long term disaster recovery and can help move Hyper-V VM to another host.
Snapshots are not enough for disaster recovery. Hyper-V VM backup is the effective way to prevent data loss. Try Vinchin Backup & Recovery to easily make VM backup with many advanced features.
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