Backups started to fail again (overall status: failure, but both snapshot and transfer returns success)
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Did anyone ever find a true resolution to this? I'm seeing a similar situation where a remote works just fine until I initiate a backup job.
Mounted a remote via NFS (v4), generated 260G of random data (using a simple dd command just to prove I can write something to the share) but when I initiate a backup job it hangs up after <10G of backup data is transferred. Sometimes it will pause for several minutes then allow a little bit more through, but it will also sometime just hang there for hours.
Latest XO commit (70d59) on a fully updated but mostly vanilla Debian 12, XCP-ng 8.3 with latest patches as of today (Aug 17, 2025). Remote target is a Synology DS1520+ with latest patches applied. Only a 1G connection, but the network is not busy by any means.
Moments before the backup 'df' and 'ls' of the respective directory worked fine. After the backup is initiated and appears to pause with <10G transferred, both commands lock up. Job in XCP-ng also seems to not want to let go.
root@xo:~# date ; df -h Sun Aug 17 10:20:45 PM EDT 2025 Filesystem Size Used Avail Use% Mounted on udev 3.9G 0 3.9G 0% /dev tmpfs 794M 572K 793M 1% /run /dev/mapper/xo--vg-root 28G 5.3G 22G 20% / tmpfs 3.9G 0 3.9G 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock /dev/xvda2 456M 119M 313M 28% /boot /dev/mapper/xo--vg-var 15G 403M 14G 3% /var /dev/xvda1 511M 5.9M 506M 2% /boot/efi tmpfs 794M 0 794M 0% /run/user/1000 192.168.32.10:/volume12/XCPBackups/VMBackups 492G 17M 492G 1% /run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7 root@xo:~# date ; ls -lha /run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7/ Sun Aug 17 10:21:23 PM EDT 2025 total 0 drwxrwxrwx 1 1027 users 56 Aug 17 22:20 . drwxr-xr-x 3 root root 60 Aug 17 22:20 .. -rwxrwxrwx 1 1024 users 0 Aug 17 22:20 .nfs000000000000016400000001 root@xo:~# date ; df -h Sun Aug 17 10:22:28 PM EDT 2025 ^C root@xo:~#[22:19 xcp05 ~]# date ; xe task-list Sun Aug 17 22:20:00 EDT 2025 [22:20 xcp05 ~]# date ; xe task-list Sun Aug 17 22:22:49 EDT 2025 uuid ( RO) : 8c7cd101-9b5e-3769-0383-60beea86a272 name-label ( RO): Exporting content of VDI shifter through NBD name-description ( RO): status ( RO): pending progress ( RO): 0.101 [22:22 xcp05 ~]# date ; xe task-cancel uuid=8c7cd101-9b5e-3769-0383-60beea86a272 Sun Aug 17 22:23:13 EDT 2025 [22:23 xcp05 ~]# date ; xe task-list Sun Aug 17 22:23:28 EDT 2025 uuid ( RO) : 8c7cd101-9b5e-3769-0383-60beea86a272 name-label ( RO): Exporting content of VDI shifter through NBD name-description ( RO): status ( RO): pending progress ( RO): 0.101I'm only able to clear this task by restarting the toolstack (or host), but the issue returns as soon as I try to initiate another backup.
Host where VM resides network throughput:
Nothing in dmesg and journalctl on XO just shows the backup starting:
Aug 17 22:21:56 xo xo-server[724]: 2025-08-18T02:21:56.031Z xo:backups:worker INFO starting backupLast bit of the VM host SMlog:
Aug 17 22:22:02 xcp05 SM: [10246] lock: released /var/lock/sm/3a1ad8c0-7f3a-4c16-9ec1-e8c315ac0c31/vdi Aug 17 22:22:02 xcp05 SM: [10246] lock: closed /var/lock/sm/b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/sr Aug 17 22:22:02 xcp05 SM: [10246] lock: closed /var/lock/sm/3a1ad8c0-7f3a-4c16-9ec1-e8c315ac0c31/vdi Aug 17 22:22:02 xcp05 SM: [10246] lock: closed /var/lock/sm/lvm-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/3a1ad8c0-7f3a-4c16-9ec1-e8c315ac0c31 Aug 17 22:22:02 xcp05 SM: [10246] lock: closed /var/lock/sm/lvm-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/1fb38e78-4700-450e-800d-2d8c94158046 Aug 17 22:22:02 xcp05 SM: [10246] lock: closed /var/lock/sm/lvm-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/2ef8ae60-8beb-47fc-9cc2-b13e91192b14 Aug 17 22:22:02 xcp05 SM: [10246] lock: closed /var/lock/sm/lvm-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/lvchange-p Aug 17 22:22:36 xcp05 SM: [10559] lock: opening lock file /var/lock/sm/b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/sr Aug 17 22:22:36 xcp05 SM: [10559] LVMCache created for VG_XenStorage-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c Aug 17 22:22:36 xcp05 fairlock[3358]: /run/fairlock/devicemapper acquired Aug 17 22:22:36 xcp05 fairlock[3358]: /run/fairlock/devicemapper sent '10559 - 625.897991605' Aug 17 22:22:36 xcp05 SM: [10559] ['/sbin/vgs', '--readonly', 'VG_XenStorage-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c'] Aug 17 22:22:36 xcp05 SM: [10559] pread SUCCESS Aug 17 22:22:36 xcp05 fairlock[3358]: /run/fairlock/devicemapper released Aug 17 22:22:36 xcp05 SM: [10559] Entering _checkMetadataVolume Aug 17 22:22:36 xcp05 SM: [10559] LVMCache: will initialize now Aug 17 22:22:36 xcp05 SM: [10559] LVMCache: refreshing Aug 17 22:22:36 xcp05 fairlock[3358]: /run/fairlock/devicemapper acquired Aug 17 22:22:36 xcp05 fairlock[3358]: /run/fairlock/devicemapper sent '10559 - 625.93107908' Aug 17 22:22:36 xcp05 SM: [10559] ['/sbin/lvs', '--noheadings', '--units', 'b', '-o', '+lv_tags', '/dev/VG_XenStorage-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c'] Aug 17 22:22:37 xcp05 SM: [10559] pread SUCCESS Aug 17 22:22:37 xcp05 fairlock[3358]: /run/fairlock/devicemapper released Aug 17 22:22:37 xcp05 SM: [10559] lock: closed /var/lock/sm/b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/sr Aug 17 22:32:51 xcp05 SM: [14729] lock: opening lock file /var/lock/sm/b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/sr Aug 17 22:32:51 xcp05 SM: [14729] LVMCache created for VG_XenStorage-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c Aug 17 22:32:51 xcp05 fairlock[3358]: /run/fairlock/devicemapper acquired Aug 17 22:32:51 xcp05 SM: [14729] ['/sbin/vgs', '--readonly', 'VG_XenStorage-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c'] Aug 17 22:32:51 xcp05 fairlock[3358]: /run/fairlock/devicemapper sent '14729 - 1240.916404088' Aug 17 22:32:51 xcp05 SM: [14729] pread SUCCESS Aug 17 22:32:51 xcp05 fairlock[3358]: /run/fairlock/devicemapper released Aug 17 22:32:51 xcp05 SM: [14729] Entering _checkMetadataVolume Aug 17 22:32:51 xcp05 SM: [14729] LVMCache: will initialize now Aug 17 22:32:51 xcp05 SM: [14729] LVMCache: refreshing Aug 17 22:32:51 xcp05 fairlock[3358]: /run/fairlock/devicemapper acquired Aug 17 22:32:51 xcp05 fairlock[3358]: /run/fairlock/devicemapper sent '14729 - 1240.953398589' Aug 17 22:32:51 xcp05 SM: [14729] ['/sbin/lvs', '--noheadings', '--units', 'b', '-o', '+lv_tags', '/dev/VG_XenStorage-b6ee0b6d-5093-b462-594f-ba2a3c3bd14c'] Aug 17 22:32:52 xcp05 SM: [14729] pread SUCCESS Aug 17 22:32:52 xcp05 fairlock[3358]: /run/fairlock/devicemapper released Aug 17 22:32:52 xcp05 SM: [14729] lock: closed /var/lock/sm/b6ee0b6d-5093-b462-594f-ba2a3c3bd14c/srLooking for other ideas.
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@jimmymiller said in Backups started to fail again (overall status: failure, but both snapshot and transfer returns success):
After the backup is initiated and appears to pause with <10G transferred, both commands lock up. Job in XCP-ng also seems to not want to let go.
You mean it's stuck in XOA?
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@olivierlambert This particular instance is a compiled version of XO, but yes, it's XO that locks up. I'd be all over submitting a ticket if this was in XOA.
Mind you I can trigger the lock up immediately after I had sent 250G of dummy data (using dd if=/dev/random) to the exact same directory using the exact same XO. I simply deleted that dummy data, kicked off the backup job, and boom, ls & df lock up after just a few minutes.
Separately on the host, the xe export task will just sit there. Sometimes some progress will happen, other times it will sit there for days w/o any progress.
I've tried rebuilding XO from scratch (without importing an older XO config) and it happens the exact same way on the newer XO. Tried creating a separate empty volume on the Synology and a different NFS export / remote--same problem. I'm at the point of trying to rebuild the XCP-ng hosts, but I'm not really sure if that's the problem because the hosts seem happy up until I kick off the backup job. VMs can migrate; there are only local SRs, so we aren't dealing with any type of storage connection problem apart from the NFS for backups and these are two different hosts (Dell PowerEdge R450s). The only common thing I can find is that the hosts are in the same pool, the backup target hardware has remained unchanged, and they reside on the same physical network (Ubiquiti-based switches) I might try rebuilding these hosts and carving out a dummy virtual TrueNAS instance just to see if I can get a different result but I'm out of ideas on things to try after that.
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All of that smells an NFS problem (or network problem) unrelated to XO itself (or XCP-ng), or on the NFS server
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try downgrading your nfs to use version 3. I think version 4.x has performance issues.
in you settings-->remote, you can edit the nfs mount for backups and add in the -o options section.I dont know the exact command but you can try using nfsvers=3 and see if that helps.
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Excellent suggestion
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@olivierlambert & @marcoi The option is 'vers=3' w/o quotes.
I tried this recommendation and made some progress in that 'ls' and 'df' don't lock up, but the export still seems to hang.
Below is a screenshot of network throughput on the XO. The plateau on the left is a 'dd if=dev/random' to a 'dummyData.txt' before the backup is kicked off. I then stop the dd and kick off the backup job (middle). After about a minute, the job hangs. I can still 'ls' and 'df' at this point, which is good, but the export job just seems stuck at 22% ('xe task-list' below). For the heck of it I tried another 'dd if=/dev/random' this time to a dummyData2.txt, which is what that plateau is on the right. While this dd is underway the backup is still supposed to be ongoing. So the directory is still writeable, but the job is just hanging up?
The number where the job hangs seems to vary too -- sometimes it will go ~30%, other times it stops at 10%. I left a job of this exact VM running last night and it actually finished, but it took 5 hrs to move 25G according to the backup report. I took <6 minutes to move 40G with the simple inefficient 'dd' command. Granted XO might be pulling (from the host) and pushing (to the NFS remote) simultaneously, but 5 hours doesn't seem right.
XO output before and while backup is ongoing:
root@xo:/run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7# ls -lha total 0 drwxrwxrwx 1 1027 users 56 Aug 18 13:12 . drwxr-xr-x 3 root root 60 Aug 18 13:11 .. -rwxrwxrwx 1 1024 users 0 Aug 18 13:11 .nfs000000000000017400000001 root@xo:/run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7# dd if=/dev/random of=/run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7/dummyData.txt bs=1M ^C36868+0 records in 36868+0 records out 38658899968 bytes (39 GB, 36 GiB) copied, 368.652 s, 105 MB/s root@xo:/run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7# df -h Filesystem Size Used Avail Use% Mounted on udev 3.9G 0 3.9G 0% /dev tmpfs 794M 584K 793M 1% /run /dev/mapper/xo--vg-root 28G 5.3G 22G 20% / tmpfs 3.9G 0 3.9G 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock /dev/xvda2 456M 119M 313M 28% /boot /dev/mapper/xo--vg-var 15G 403M 14G 3% /var /dev/xvda1 511M 5.9M 506M 2% /boot/efi tmpfs 794M 0 794M 0% /run/user/1000 192.168.32.10:/volume12/XCPBackups/VMBackups 492G 42G 451G 9% /run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7 root@xo:/run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7# ls -lha total 37G drwxrwxrwx 1 1027 users 164 Aug 18 13:20 . drwxr-xr-x 3 root root 60 Aug 18 13:11 .. -rwxrwxrwx 1 1024 users 37G Aug 18 13:20 dummyData.txt -rwxrwxrwx 1 1024 users 0 Aug 18 13:11 .nfs000000000000017400000001 -rwxrwxrwx 1 1024 users 0 Aug 18 13:20 .nfs000000000000017700000002 drwxrwxrwx 1 1024 users 154 Aug 18 13:20 xo-vm-backups root@xo:/run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7# cd root@xo:~# df -h Filesystem Size Used Avail Use% Mounted on udev 3.9G 0 3.9G 0% /dev tmpfs 794M 584K 793M 1% /run /dev/mapper/xo--vg-root 28G 5.3G 22G 20% / tmpfs 3.9G 0 3.9G 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock /dev/xvda2 456M 119M 313M 28% /boot /dev/mapper/xo--vg-var 15G 404M 14G 3% /var /dev/xvda1 511M 5.9M 506M 2% /boot/efi tmpfs 794M 0 794M 0% /run/user/1000 192.168.32.10:/volume12/XCPBackups/VMBackups 492G 42G 450G 9% /run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7 root@xo:~# ls -lha /run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7 total 37G drwxrwxrwx 1 1027 users 164 Aug 18 13:20 . drwxr-xr-x 3 root root 60 Aug 18 13:11 .. -rwxrwxrwx 1 1024 users 37G Aug 18 13:20 dummyData.txt -rwxrwxrwx 1 1024 users 0 Aug 18 13:11 .nfs000000000000017400000001 -rwxrwxrwx 1 1024 users 0 Aug 18 13:20 .nfs000000000000017700000002 drwxrwxrwx 1 1024 users 154 Aug 18 13:20 xo-vm-backups root@xo:~# dd if=/dev/random of=/run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7/dummyData2.txt bs=1M ^C7722+0 records in 7722+0 records out 8097103872 bytes (8.1 GB, 7.5 GiB) copied, 78.9522 s, 103 MB/s root@conductor:~# ls /run/xo-server/mounts/1f33cf95-36d6-4c5b-b99f-71bb47008dd7 dummyData2.txt dummyData.txt xo-vm-backups[13:32 xcp05 ~]# xe task-list uuid ( RO) : ba902e8a-7f08-9de9-8ade-e879ffb35e11 name-label ( RO): Exporting content of VDI shifter through NBD name-description ( RO): status ( RO): pending progress ( RO): 0.222Any other ideas before I go down the route of trying to carve out a virtual NAS instance?
Thanks again for your input.
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@jimmymiller
step 1 - reboot xo, xcp host and nas. Try just the backup again.
if step 1 fails then step 2- Clone the vm so you have a test to play with. setup a new remote to another path on nas using ver=3 command. Then setup a new backup job just for that one vm and test backup without any other testing like using dd.you need to first confirm your setup works using the separate testing above.
its possible your backups got messed up somehow (permissions/files) and once you confirm your setup is working or not we can figured out possible next steps.
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@marcoi I've definitely been through all those steps before, but I'll try it again. The VM in question is a test machine I built specifically for this troubleshooting and I've rebuilt this XO three times, including not bringing over any export / configurations / backups from previous installments--I simply pointed a vanilla XO (running similar code) at the same XCP-ng pool. I've created a different volume and NFS export on the Synology, so that even started blank and each time I've gone through the test I've preemptively emptied the directories before connecting the XO to the NFS export. The only two things I haven't tried are rebuilding the XCP-ng host from scratch, nor have I tried sending to a different physical remote. Guess it's time to start down that path.
The fact that I can write data to the NFS mount from within the XO VM even while the XCP-ng export is in progress is the part that gets me and makes me think this might be a XO problem vs. an underlying infrastructure problem. Oh well, time to try rebuilding these.
Hammer down!
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@jimmymiller i just noticed one of your pics of the backup had NDB enabled. (says exporting content of VDI shifter through NBD.
Can you check in your backup job if NDB is on?
I would turn it on and off a few times and leave it off then save the job and retry. There was issues with NDB gui in prior version that might be still affecting your test backup job.
