@stormi
should have been and and not or.
so
and then update with iso 8.3 Of.
Had an old server that kept crashing during the 8.3 Of. installation. It worked with RC1 and then upgraded to 8.3 Of.
Sometime this old things are a bit tricky

Hello,
I also had problems installing Beta 2 on older servers.
Switch from BIOS to UEFI under Boot in the BIOS.
Take a USB stick with the RC1, install and update with yum update
or
just use the new 8.3 Official.

@olivierlambert
Unfortunately, I don't have much time in the next few days.
On Sunday I will reset one of the pools with the error to NBD / CBT Delta Backup and then pull the logs and compare them with the one from the working 9.3. Let's see if I can see anything there. If not, I will send you the logs. I will also take a closer look at which processes are stuck there. It looks to me like there are ghost processes running there that don't terminate but seem to continue to block the snapshot. That also seems to be the reason why the snapshot cannot be deleted, except after a reboot.
If I have time, I will also set up a new pool with 9.3 RC2 and then update it to 9.3 officially via yum, just to see if it can then also do error-free NBD deltas.
Regards Joerg

@Tristis-Oris @Mathieu
Hello, I'm glad I could help you, but it would be nice if the NBD worked. I was able to save a lot of space on the storage with NBD and CBT. I hope that in the not too distant future it will work again like in 8.2.1
My 8.3 LAB pool, updated with yum, made an error-free delta backup with NBD and CBT last night, just like my last 8.2.1 pool.
regards Joerg

Status quo:
I have now reduced the problem to the NBD.
With an NBD full backup, everything seems to be working.
With a delta backup, NBD leaves snapshots that are blocked by the control domain of the various Xen servers. These can only be disconnected/forgotten and then deleted after a reboot of the hole pool or individual reboot of all Xen servers in the pool. The last option at least gives you the chance of a reboot without shutting down all VMs, if the pool has several Xen servers. But all servers in the pool must be rebooted.
Unfortunately, an xe-tool restart is not enough.
The activation/deactivation of CBT does not matter.
All backups without NBD run without errors.
This error occurs on all Xen servers installed from USB Image 8.3 officially. My lab pool, which was updated from 8.3RC2 to 8.3 Official via yum, doesn't seem to have the problem. 1 full backup and 4 delta backups ran without errors and without blocked snapshots.

As I urgently need a current backup, I deactivated all NBD backups and set the server interface back to NO NBD. The standard delta backups are now running without errors again.

I left my LAB pool on NBD with CBT to see if the error occurs there in the next few days.

I actually wanted to create a new topic for the problem, but I'm not really sure which category I should put it under.

@Tristis-Oris Not in your case?

In the Release Information about 8.3 you can read:
"Users who installed a prerelease of XCP-ng 8.3 must upgrade to the final 8.3.0 version using the installation ISO image. The only exception is for users who installed XCP-ng 8.3 RC2 or have already upgraded to RC2 using the installation ISO image. These users can simply update their system without needing the ISO image."

@stormi
Test with removed the NDB and CBT in the backup and removed the NBD interface in the pool.
Fullbackup Okay
Multiple delta backups all Okay no errors.
The error lies in the NBD or CBT.
But why not on the pool updated with yum from 8.3 RC2 ????

Can someone create a new topic?

@stormi
Of course, you shouldn't have a VM on the local storage.
It's also a good idea to write down the IPs, MACs and the number of the NICs beforehand. It can happen during the new installation that the order of the network cards changes.
Final tip: if you use iSCSI storage and use the iSCSI IQN as identification, you should also write this down beforehand and set it on the newly installed server before you put the server in the pool, otherwise you will have problems with the iSCSI storage.

@stormi
Sorry, I was a bit confused this morning when I saw all the errors. Of course it wasn't an update to 8.3 RC but to 8.3.0 Official.
Very strange thing, I checked my test lab server, it's the only pool that doesn't have the error. Full backup and several delta backups, all OK.
The only difference between this and the other pools is that this one was running with 8.3 RC2 and was only updated to 8.3.0 official with yum update.
I have now cleaned a faulty pool, removed all snapshots, removed the NDB and CBT in the backup and removed the NBD interface in the pool. I'm currently doing a full backup on this pool and will then do several deltas to narrow down the error a bit.
Regards, Joerg

I saw that Tristis Oris seems to have a similar problem with snapshots.

Something else, when updating from 8.2.1 to 8.3 RC.
My 8.2.1 servers were still running on BIOS boot. When updating to 8.3 RC I got the message that there was still a DOS table on the hard drive and the update from the USB stick was aborted.
A newly installed 8.3 server with UEFI cannot be integrated into the old 8.2 pool.

Here is a small workaround:
2 USB sticks, one with 8.2.1 and one with 8.3 RC.
Take one server out of the pool, not the master.
Reinstall with UEFI on 8.2.1.
Integrate server into the old pool.
make server as new pool master.
The server can now be updated to 8.3 without any problems, the master is on UEFI and all pool information and VM are on 8.3.
Now just take all other servers out of the pool, do a clean 8.3 UEFI installation and put them back into the pool.

Maybe that will help others with the same problem.

regards Joerg

Version XCP-NG 8.3 RC
XO lastest version

Hello,
I use XO with Delta Backup to back up my VM's. I have activated NBD and CBT in the backup. The backups run via the management interface with NBD activated.
The first full backup runs error-free.
The second backup with delta gives me the error message cleanVm: incorrect backup size in metadata and VDI_IN_USE and the backup ends with an error.
After the delta backup, I then have snapshots on the storage that are blocked with "Control domain on host xxx". I can then no longer delete these. The only option is to reboot all Xen servers in the pool, after which the snapshots are still there, but can then be disconnected and forget to get them deleted.
I was able to reproduce this error on different pools with different servers, all 8.3. It is always different VMs that trigger the error and others that are backed up without errors.
If I delete all control domain blocked snapshots and also the purged snapshot from the storage, the next full backup runs error-free again.
Does anyone have the same problem and maybe a solution?
regards Joerg

@olivierlambert
Hello,
I created a new SR and installed a new VM and
installed a new XO.
The last one was definitely the answer.
It's working now, so as far as backup via XO goes.
I tested everything extensively, with different VM, SR and different drive fill levels, all ok.
A manual snapshot won't work, but that's what it is.
My old XO installation, unfortunately I didn't write down the version, was from January. Also, when I reinstalled, I switched from stable to latest as you indicated.
Unfortunately, I can't say whether the pure stable update or the change to latest was the solution.
But the main thing is a happy ending.
Greetings Joerg

@olivierlambert
by the way: which version of XO are you using, not that I am using an older one and that the cause is there.
My drives are also local LVM so should be "Thick" too.

@olivierlambert
I will make a retry of the test.
Is the drive empty or filled with data
If the disk are empty it works for me to.

@olivierlambert
Seems like that to me too. Let me know if you found a solution. I leave the test VM on my Xen server so that I can test again at any time.

@olivierlambert
Exactly, it looks like the snapshot of the entire VM is always calculated first. If there is enough space then only the selected drive is taken in the backup, if not the Backup is aborted.
In other words, only if you can take a manual snapshot of the VM, XO's backup will then only backup the selected drive.
It would be good if the backup only checked whether there was enough space for a snapshot of the selected drive.

@olivierlambert
Here as promised a test of the [NOBAK] function.

About the SR:
NVME Raid
Size: 2.4 TB used of 5.5 TB total (2.9 TB allocated)

About "SRV-Test" VM:
0 "SRV-Test" "NVME Raid" 50GB /dev/xvda
1 "[NOBAK] SRV-Test Drive" "NVME Raid" 1.5 TB /dev/xvdb

Manual snapshot takes both drives and ignores the [NOBAK]
Backup via Xo works, only the first drive is backed up.
You can follow this under TASKS in the XO.
Under "File Restore" in the XO there are no data for the second drive.

So beautiful - so good. The idea would actually be to back up a server with very large drives partially.

So I change my VM to the following:
0 "SRV-Test" "NVME Raid" 50GB /dev/xvda
1 "[NOBAK] SRV-Test Drive" "NVME Raid" 1.5 TB /dev/xvdb
2 "[NOBAK] SRV-Test second test drive" NVME raid 2 TB /dev/xvdc

My SR looks know:
NVME Raid
4.4 TB used of 5.5 TB total (4.9 TB allocated)

Exactly the same result as the first test, both with the manual snapshot and with the XO backup.
Actually, the manual snapshot should not work at all, because there is not enough space on the SR to include all the drives, but due to thin provisioning it works because the drives are almost empty.

Now I'm filling the drives with data so I'm sure there isn't enough space on the SR for a full snapshot of all the data.

As expected, I get the error message "The specified storage repository has insufficient space" when taking a manual snapshot Everything is understandable since the manual snapshot saves the entire VM and there is no space for the 3.5 TB snapshot on the SR.

Now I make another backup with XO, which previously only backed up the 50 GB of the first drive.
UPS ... After a few seconds, the error "SR_BACKEND_FAILURE_44(, There is insufficient space, )" and the backup was aborted.

So, XO seems to first test whether a complete backup/snapshot can be created with all drives and then backs up the 50 GB of the first drive.
In my opinion a bit suboptimal because it doesn't solve the problem to always have twice the space on the SR as you used, even if I only want to back up the system disk of a VM with a few GB, for example.

Conclusion of the test:
A) Manual Snapshot with only part of drives ([NOBAK]), does not work.
B) Backup with XO with only part of the drives ([NOBAK]), works, but only if there is enough space for a complete snapshot of the VM on the SR.

Hope you can use with my little test for something.

@olivierlambert
I'm trying that this weekend.
Thanks in advance.

@olivierlambert

Great relief, I was beginning to have doubts about myself

@olivierlambert
Hmmm. Tried rename the Disk "SRV-File-Debian-10.10" in "[NOBAK] SRV-File-Debian-10.10"
It does not work!