Feature Request: Would it be possible to specify a delay between "Number of retries if VM backup fails"? Last night there was an internet outage that affected many of my clients s3 backups. I noticed that the retries I had specified all happened immediately after the internet failure with no delay between them. Because the internet was not restored they all failed too. It would be good to set a delay between retries to allow time for the internet to be restored. Today I manually restarted all the failed backups.
Thanks.

@abudef Yes, data blocks is enabled on the remote.

@abudef I just had a backup failure. This triggered a full (key) backup on the next run which transferred 165GiB. When I rdpd into the vm I could see that the vm contained 345GiB of data including the system drive. I conclude, therefore that compression is working for full key backups at a ration of around 2:1.
I hope this helps.

@olivierlambert <The snapshot is deleted. You need a reference point to do differential>. So, since the snapshot is deleted, create a new one (snapshot) as part of the restore process and use that for the reference - then delete it when done.

@olivierlambert Agreed, but in the case where the snapshot has been deleted, why can't the differential restore process simply create a snapshot from the vm and use that instead?

@olivierlambert So, earlier in this thread, florent said "differential restore work by not transferring the data that the snapshot and the backup have in common, without reading any of those
it clone the last snapshot, an then revert the block changed between the older backup and the snapshot". If this is true (and I'm sure it is) why can't the differential restore system create the missing snapshot and use that to complete the differential restore?

@olivierlambert No, not recreating the snapshot from the CBT metadata but simply creating a new temporary snapshot, perform differential restore and delete the temporary snapshot when done.

@frank-s So- I have been thinking about this. If an NBT/CBT backup is set to destroy the snapshot, would it be possible to make differential restore work by having the restore process create the snapshot it needs, perform the differential restore and then delete the snapshot?

Thank you.

Thank you. Is there somewhere I can read about this instant restore feature?

@frank-s Soz - I meant differential restores...

@florent
I just did a delta backup on a small VM but chose NOT to delete the snapshot. It completed quickly and I then tried a differential restore and it worked. I also tried to do a differential restore on a delta backup made yesterday when the snapshot was deleted - this also worked. Will it be possible in the future to make differential backups work without keeping the snapshot? Is such a thing possible?
Thanks,
Frank.

I will backup again without deleting the snapshot and then attempt a differential restore.
I will update this thread when done.

So my guess is it will work if I choose not to delete the snapshot??? If that is correct it is a pity as differential restore is very fast compared to regular restore. Differential restore, for instance, would be a brilliant way to recover quickly from a ransomware attack. Also, deleting the snapshot makes coalescing much faster. Am I correct in my assumptions? Is there a way it could be made to work without the snapshot?
Thank you,
Frank.

@olivierlambert
I am using XO from the sources.
commit a9b99 Master, commit 30172
When I try to restore I select the appropriate backup (I have done this with both internal NFS remote and also with s3 remote). I select the SR that the backed up VM is on and turn on "use differential restore". When I click OK it fails immediately with the following error: <VDI_INCOMPATIBLE_TYPE(OpaqueRef:6ef1574a-ffc6-412b-bf6b-6804bacc0523, CBT metadata)>
This also happens on a completely different installation (different XCP different XO different client).
It's been a while since I used differential restore. It seems odd that when turned on I can select any destination SR. My understanding is that the restore needs the same SR as the original VM - that's what I selected.
When I last used differential restore I was not using NBD/CBT.
Regular restore seems to be working.

Thanks,
Frank.

When I try to perform a differential restore I get this error:
VDI_INCOMPATIBLE_TYPE(OpaqueRef:94df0a4b-69ba-4ef5-adb3-21c5259ea0b1, CBT metadata)
Regular restore appears to be working.
Any advice please?

Hi, I am running from the sources and I'm almost up to date (991b4) . Can anyone please tell me what this means "Error: can't create a stream from a metadata VDI, fall back to a base". Restarting the backup results in a full backup rather than an incremental.
Thanks.

@florent Thank you for the update.

@florent Hi, Have you been able to make any progress with this?
Thanks.

Thanks for your replies. Since the advent of mirror backups I realised there was an opportunity to backup to several different USB disks where each disk is a different remote allowing rotation of the disks. The primary backup goes to additional internal storage which is then mirrored to the USB disks. Only one snapshot per vm is needed regardless of how many USB disks are in use. To do this I need to script the mounting process for these disks and send notification emails when a disk is mounted, unmounted (safe to unplug) or when no disk could be found.
This is my use case.
Thanks