VM Snapshots

[dpearceFL]

Yes, I know snapshots are not backups...

In VSphere/ESXi, snapshots continue to grow as more and most data is changes since the last snapshot. VMware documentations says to not keep snapshots around for more than 3-5 days. If you go too long, coalescing (merging) the snapshot into the original disk can take a loooong time and even be impossible without some heroics.

Does Proxmox have the same limitation? How long can you keep them around safely?

 

[fiona]

Hi,
I'm not aware of any such limitation. Rollback to a snapshot should always work no matter how old it is. Your disks will need more size depending on how much delta for the snapshot needs to be saved of course and rollback might take a bit longer, but at most the time it takes to write back that delta. All the details depend on the underlying storage, but there is no really no need to remove snapshots after a few days, except if you have limited space on the storage.

 

[dpearceFL]

Thank you for this information.

Another question: Are the snapshots stored in the qcow2 file? Where are they stored? I'm using a NFS storage.

 

[fiona]

Thank you for this information.

Another question: Are the snapshots stored in the qcow2 file? Where are they stored? I'm using a NFS storage.

The part of the snapshot that remembers the state of the disk will be in the qcow2 file. If you include RAM, you will get an additional state file (by default on the same storage as the disk). The state file is fixed in size and will never change after taking the snapshot.

 

[dpearceFL]

So if the snapshots are stored in the qcow2 file, if I go crazy and create 100 snapshots (assuming lots of file activity in the OS), will the snapshots eventually fill up the qcow2 file and crash the OS? Or will the qcow2 file grow in size?

 

[dpearceFL]

The qcow2 file does grow! Does not seem to shrink by itself.

 

[dpearceFL]

If you move the storage, it will recover the space.