NFS share: Problem with snapshot backups

[ke992]

Hello,

I have a problem with snapshot backups to an nfs share. At the end of the backup process, the virtual machine freezes and is no longer reachable.
Backup process needs 2 minutes for the last 11 percent.

proxmox ve 8.4.1 (no-sub repository) with zfs. nfs is v4.

backup log:

INFO: starting new backup job: vzdump 100 --storage nfs-share --compress 0 --node host01 --remove 0 --notes-template '{{guestname}}' --notification-mode auto --mode snapshot
INFO: Starting Backup of VM 100 (qemu)
INFO: Backup started at 2025-04-17 22:06:17
INFO: status = running
INFO: VM Name: test
INFO: include disk 'scsi0' 'local-zfs:vm-100-disk-0' 120G
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: creating vzdump archive '/mnt/pve/nfs-share/dump/vzdump-qemu-100-2025_04_17-22_06_17.vma'
INFO: started backup task '2bfc8dba-a41a-4af4-b5eb-f1b32c7f1987'
INFO: resuming VM again
INFO:   3% (4.7 GiB of 120.0 GiB) in 3s, read: 1.6 GiB/s, write: 1.4 GiB/s
INFO:   7% (9.2 GiB of 120.0 GiB) in 6s, read: 1.5 GiB/s, write: 1.4 GiB/s
INFO:  13% (16.6 GiB of 120.0 GiB) in 9s, read: 2.5 GiB/s, write: 1.0 GiB/s
INFO:  26% (31.7 GiB of 120.0 GiB) in 12s, read: 5.0 GiB/s, write: 0 B/s
INFO:  38% (46.5 GiB of 120.0 GiB) in 15s, read: 5.0 GiB/s, write: 0 B/s
INFO:  51% (61.6 GiB of 120.0 GiB) in 18s, read: 5.0 GiB/s, write: 0 B/s
INFO:  63% (76.7 GiB of 120.0 GiB) in 21s, read: 5.0 GiB/s, write: 0 B/s
INFO:  76% (91.9 GiB of 120.0 GiB) in 24s, read: 5.1 GiB/s, write: 0 B/s
INFO:  89% (107.3 GiB of 120.0 GiB) in 27s, read: 5.1 GiB/s, write: 0 B/s
INFO: 100% (120.0 GiB of 120.0 GiB) in 2m 10s, read: 126.7 MiB/s, write: 5.9 MiB/s
INFO: backup is sparse: 107.90 GiB (89%) total zero data
INFO: transferred 120.00 GiB in 130 seconds (945.2 MiB/s)
INFO: archive file size: 12.12GB
INFO: adding notes to backup
INFO: Finished Backup of VM 100 (00:02:10)
INFO: Backup finished at 2025-04-17 22:08:27
INFO: Backup job finished successfully
INFO: notified via target `mail-to-root`
TASK OK

system log:

Apr 17 22:06:17 host01 pvedaemon[5318]: INFO: starting new backup job: vzdump 100 --storage nfs-share --compress 0 --node host01 --remove 0 --notes-template '{{guestname}}' --notification-mode auto --mode snapshot
Apr 17 22:06:17 host01 pvedaemon[5318]: INFO: Starting Backup of VM 100 (qemu)
Apr 17 22:06:43 host01 pvedaemon[2765]: <root@pam> starting task UPID:host01:000015B0:000094F0:68015F53:vncproxy:100:root@pam:
Apr 17 22:06:43 host01 pvedaemon[5552]: starting vnc proxy UPID:host01:000015B0:000094F0:68015F53:vncproxy:100:root@pam:
Apr 17 22:06:57 host01 pvedaemon[2765]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:04 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:04 host01 pvestatd[2749]: status update time (8.255 seconds)
Apr 17 22:07:11 host01 pveproxy[2781]: proxy detected vanished client connection
Apr 17 22:07:14 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:15 host01 pvestatd[2749]: status update time (8.304 seconds)
Apr 17 22:07:22 host01 pvedaemon[2765]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:24 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:24 host01 pvestatd[2749]: status update time (8.301 seconds)
Apr 17 22:07:34 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:34 host01 pvestatd[2749]: status update time (8.264 seconds)
Apr 17 22:07:44 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:44 host01 pvestatd[2749]: status update time (8.258 seconds)
Apr 17 22:07:46 host01 pvedaemon[2765]: <root@pam> end task UPID:host01:000015B0:000094F0:68015F53:vncproxy:100:root@pam: OK
Apr 17 22:07:47 host01 pvedaemon[2763]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:55 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:07:55 host01 pvestatd[2749]: status update time (8.260 seconds)
Apr 17 22:08:04 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:08:04 host01 pvestatd[2749]: status update time (8.261 seconds)
Apr 17 22:08:14 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:08:14 host01 pvestatd[2749]: status update time (8.254 seconds)
Apr 17 22:08:24 host01 pvestatd[2749]: VM 100 qmp command failed - VM 100 qmp command 'query-proxmox-support' failed - unable to connect to VM 100 qmp socket - timeout after 51 retries
Apr 17 22:08:24 host01 pvestatd[2749]: status update time (8.177 seconds)
Apr 17 22:08:27 host01 pvedaemon[5318]: INFO: Finished Backup of VM 100 (00:02:10)
Apr 17 22:08:27 host01 pvedaemon[5318]: INFO: Backup job finished successfully
Apr 17 22:08:27 host01 perl[5318]: notified via target `mail-to-root`
Apr 17 22:08:27 host01 postfix/pickup[2660]: AEAEB19081: uid=0 from=<root>
Apr 17 22:08:27 host01 pvedaemon[2764]: <root@pam> end task UPID:host01:000014C6:00008AF5:68015F39:vzdump:100:root@pam: OK

Any ideas?