Windows deduplication, spanned volumes on dynamic disks and PBS...

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christophe

Renowned Member
Mar 31, 2011
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Hi all,

It seems PBS 3.0 is able to file-restore files from a deduplicated ntfs Windows 2022 VM. This is great! PBS 2.x was NOT able to do so.
I haven't seen this feature in any doc yet, but more and more of our users are happy.
Is someone from proxmox team aware of that? ;)

It seems PBS 3.0 is able to file-restore files from a spanned volume on a dynamic disk (ntfs again) Windows 2022 VM. This is great! PBS 2.x was NOT able to do so!
Is someone from proxmox team aware of that? ;)

We haven't tried yet stripped volumes but may be are they also ok for a native file-restore with PBS 3.x?

It is not easy to find info on such features, neither at kernel level, nor at PBS level.

Can anyone confirm those facts?

So as of now, ReFS is the last remaining filesystem on Windows that needs a dedicated VM to restore files.

Thank you all, PBS is great!

Christophe.
 
the restore image kernel was updated for PBS 3.0, possibly the NTFS driver supports more features now..
 
christophe said:
So nobody was really aware...
Well, no problem : it works!

Christophe.
Click to expand...
I've been trying to test with updated PBS (3.1-4) and PVE (8.1.10) as well, but using an existing backup of Windows Server 2019 with deduplication. It seems to still not be working. Did you use a fresh backup?
 
hydrogencn said:
I've been trying to test with updated PBS (3.1-4) and PVE (8.1.10) as well, but using an existing backup of Windows Server 2019 with deduplication. It seems to still not be working. Did you use a fresh backup?
Click to expand...
No, in fact it is not working with ntfs deduplicated volumes.
Some pve versions (depending on in kernel ntfs driver) gives an error when trying to restore, and latest versions gives no error but restored file is empty!

And don’t forget : dedup tasks on Windows volumes starts a few days after volume creation…

And bé avare that if you a restoring a file which is NOT deduplicated (on a deduplicated volume), il will work ! You need to verify in Windows if file size is very different than on disk file size!!

So one need to carefully verify what is truely restored, no error does not mean file restore ok!!!

Same problem with software raid on Windows volumes : if you are lucky and the file to restore is on the first stripe, it’s ok. If file to restore is on any other stripe, it will not work…


Christophe.
 
Last edited:
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Hy

I'm also looking for a way to restore files from Windows deduplicated disks. Does anyone know if it's possible to attach a backed-up disk to a running vm, so that Windows can mount the image with dedup-driver?

kr
Roland
 
yes, that is possible - but you need to be careful which VM you attach the disk to, to avoid confusing Windows because of duplicated IDs. it's probably best to use a dedicated VM just for this purpose.
 
You are right, aktivating a duplicate disk can cause bsod. Already happened to me with the C partition. So I always use a different vm for such restores.

Do you know how to mount the image disk from pbs to an vm on pve?

thanks Roland
 
you need to map the backup snapshot using "proxmox-backup-client map ...", and then you can use the loop device it prints as a block device to pass to a VM: "qm set XXX --scsiX /dev/loopX,snapshot=1", for example. we have some ideas how to integrate this better into PVE, maybe combined with a virtiofs share to allow transferring files from that VM to the host or another guest..
 
Ok I couldn't wait

This works
Unmount was done via gui, not sure if command with delete is correct.


Code: 
proxmox-backup-client snapshot list --repository <User>@pbs@<PBS>:8007:<Storage>
proxmox-backup-client map vm/<VmId>/<Snapshot> <Disk> --repository <User>@pbs@<PBS>:8007:<Storage>
set <VmId> --scsiX /dev/loopX,snapshot=1
qm set <VmId> --delete scsiX 
proxmox-backup-client unmap /dev/loopX

kr
Roland
 
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except for the double unmap, that looks good ;)
 
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