There is a lot that goes into backing up virtual machines.
This post will focus on making them faster by using snapshots.
I use HashBackup and VMware Workstation. But this could be applied to other backup tools and VM software as well.
What I'm using VMware for
I spend most of my time outside virtual machines.
For the most part I only use them for testing things, or occasionally when I need full linux (WSL is usually all that's needed these days.)
Backing up big files is hard
When a deduplicating backup program needs to find changes in a really big file, it must read through the entire thing. This is fine for a 10GB file, but it's a bit more time-consuming if it's 100GB.
Making it easier with snapshots
What a snapshot in VMware does is it records all file changes in a separate file from the main disk. This way the backup program only needs to read through the snapshot for changes instead of the main virtual disk file.
When to delete snapshots
Deleting a snapshot will write all recorded file changes in the snapshot to the main virtual disk file. If the snapshot is kept too long it will slow down the VM. It also takes much longer to write a lot of changes to the disk.
I usually delete snapshots after doing something that causes a lot of changes, such as a large Windows 10 update. Or for my linux VM's, if the snapshot gets around 70% of the main disk then I delete the snapshot.
That's it for now!