How perfect are VM Snapshots?

Do they perfectly restore the VM to that specific state at that specific time? Like, seconds accuracy?

I ask because I thought it'd be way easier for me in the future to pre-install all the apps in my VM and then create a snapshot before I sysprep it, in case I need to change my golden image in the future, to cut down on time much as I can, instead of re-doing the entire thing from scratch

I am using VirtualBox, a (non-Microsoft) VM.
With that, snapshot are an exact replication of the situation when the snapshot was taken.
Even the windows size is stored...

The only thing I always have to do (if I don't want a new situation remembered) is restoring the last snapshot, without making a snapshot of the new situation.

You can even restore older snapshots to recreate the situation of that snapshot. That's why I always describe what I changed or added in the note area of the snapshot. It really is very handy to use a VM to test programs or changed settings, because one always can reset to a former situation.

The build in VM of Windows I don't have experience with, but I think it will function similarly.

CSharpDev said:

Do they perfectly restore the VM to that specific state at that specific time? Like, seconds accuracy?

I ask because I thought it'd be way easier for me in the future to pre-install all the apps in my VM and then create a snapshot before I sysprep it, in case I need to change my golden image in the future, to cut down on time much as I can, instead of re-doing the entire thing from scratch

Click to expand...

snapshots are great.

However, with a VM, why not just shut down the VM, and make a backup copy of the backend file for the VM. Then you have a perfectly crash consistent copy of that VM at that exact moment in time.

pparks1 said:

snapshots are great.

However, with a VM, why not just shut down the VM, and make a backup copy of the backend file for the VM. Then you have a perfectly crash consistent copy of that VM at that exact moment in time.

Click to expand...

Good answer but snapshots are like differential / incremental backups and can be taken very quickly or at least faster than full backups --depending on the size of the VM. Of course the snapshot file can get quite large too - so it's worth keeping an eye on it and removing older snapshots from time to time.

You still need a full backup from time to time in case you ever need to do a "bare metal restore" rather than have to re-install the whole vm again plus any applications you have running in the guest.

Treat snapshots rather like logs in big database systems. If you need to recover the DB you can often do it by "replaying" the logs rather than a full bloodied restore which might mean the loss of several days transactions.

cheers
jimbo

Are exporting the VM to a destination (Hyper-V) a perfect backup?

On my VirtualBox I had an extra Windows 11 installation, that I activated last year with a Windows7 key. That then still was possible.

I have tested if that activation is transfered together with cloning and/or exporting the 'machine'. And yes, it does, as long as you select the right options when cloning / exporting. After importing the export file again, all settings, even the window size and the activation still were there!
For cloning you need to activate: "Keep hardware UUIDs". For exporting I did not use any extra setting, although I always export with option "Write Manifest file" activated.

So yes, in VirtualBox the export is a perfect backup.
How it functions with other VMs I don't know, I suppose it will be similar.