ReFS backup deletion to regain space

[ChrisGundry]

Hi all

We have a number of ReFS repos and they have worked great, we are getting good performance with block cloning and been able to keep a lot more backups in the same amount of physical space. For example one repo is 50TB, but has 140TB of backups in it, happy days.

We allowed our retention to grow as we were getting such good returns, but now it has reached the point where we are starting to get low on disk space.

The issue I have is that when we have reduced retention and old points have been deleted we have not regained any space, none at all. If we had released just a small amount I would put it down to ReFS being amazing and block cloning doing it's thing... But I don't quite believe it to be so amazing that I can delete 1 year worth of restore points for 10 VMs and regain zero space. Perhaps it is...

I have raised the query with support and they have said everything is fine and ReFS is doing it's thing. But I wanted a 2nd opinion from anyone who wants to weigh in...

My gut is telling me that there is something like with MS DeDupe where if you delete data it still just sits in the SysVol until you run command x to clean it all up... But if that is the case my Googling is not returning the required info!

Thanks

[chris.childerhose]

From what I can see you need to be patient for ReFS to reclaim space or the other option seems to be using SDELETE as noted here - veeam-backup-replication-f2/refs-reclai ... 55541.html

[ChrisGundry]

Thanks, but it has been several weeks since the deletion and we have not observed any reclamation of space. We are only taking about space reclaimed within the Windows OS itself, so SDELETE should not apply here I believe? That would only be for passing the savings back down to a thin provisioned SAN volume/LUN I think?

[ChrisGundry]

We have today deleted some other points for another job, by reducing retention period. This has freed up some space. We deleted 19TB of backups, which only actually freed up 1.88TB of space on ReFS. So I guess it seems like ReFS is just doing a really good job and the previous deletion we did was a lot of cloned blocks so didn't free up any real space...

[Mildur]

Hi Chris

Most likely.
You could try Timothy‘s blockstat.exe.
It can be used to analyze shared blocks.
https://dewin.me/refs/

Wolfgang wrote a good summary about the tool:
https://vnote42.net/2020/10/06/analyse- ... ple-veeam/

[ChrisGundry]

Haha I found that very article/tool yesterday afternoon! I a plan to finish reading and do some checks today/tomorrow if I get time! Thanks

[chris.childerhose]

Ah yes I forgot about that tool. Very handy and works too.