Super slow, timeout, and VM stuck while backing up, after updated to PVE 9.1.1 and PBS 4.0.20

[pfornara]

So the only thing we have in common is 10 Gbps... Can you test it on a 1 Gbps?

1 Gbps backup:



INFO: starting new backup job: vzdump 201 --remove 0 --node stige --storage pbs01 --notes-template '{{guestname}}' --notification-mode auto --mode snapshot
INFO: Starting Backup of VM 201 (qemu)
INFO: Backup started at 2025-12-02 14:52:30
INFO: status = running
INFO: VM Name: SMIPRINTER
INFO: include disk 'scsi1' 'local-lvm:vm-201-disk-1' 32G
INFO: include disk 'efidisk0' 'local-lvm:vm-201-disk-0' 4M
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: creating Proxmox Backup Server archive 'vm/201/2025-12-02T13:52:30Z'
INFO: issuing guest-agent 'fs-freeze' command
INFO: issuing guest-agent 'fs-thaw' command
INFO: started backup task 'a5f1509f-cec7-4fed-982c-5a6e83682760'
INFO: resuming VM again
INFO: efidisk0: dirty-bitmap status: OK (drive clean)
INFO: scsi1: dirty-bitmap status: OK (11.7 GiB of 32.0 GiB dirty)
INFO: using fast incremental mode (dirty-bitmap), 11.7 GiB dirty of 32.0 GiB total
INFO: 1% (228.0 MiB of 11.7 GiB) in 3s, read: 76.0 MiB/s, write: 68.0 MiB/s
INFO: 3% (408.0 MiB of 11.7 GiB) in 6s, read: 60.0 MiB/s, write: 52.0 MiB/s
INFO: 4% (572.0 MiB of 11.7 GiB) in 9s, read: 54.7 MiB/s, write: 54.7 MiB/s
INFO: 6% (736.0 MiB of 11.7 GiB) in 12s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 7% (900.0 MiB of 11.7 GiB) in 15s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 8% (1.0 GiB of 11.7 GiB) in 18s, read: 56.0 MiB/s, write: 52.0 MiB/s
INFO: 10% (1.2 GiB of 11.7 GiB) in 21s, read: 53.3 MiB/s, write: 50.7 MiB/s
INFO: 11% (1.4 GiB of 11.7 GiB) in 24s, read: 57.3 MiB/s, write: 57.3 MiB/s
INFO: 13% (1.6 GiB of 11.7 GiB) in 27s, read: 64.0 MiB/s, write: 61.3 MiB/s
INFO: 14% (1.7 GiB of 11.7 GiB) in 30s, read: 60.0 MiB/s, write: 60.0 MiB/s
INFO: 16% (1.9 GiB of 11.7 GiB) in 33s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 17% (2.1 GiB of 11.7 GiB) in 36s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 19% (2.2 GiB of 11.7 GiB) in 39s, read: 57.3 MiB/s, write: 54.7 MiB/s
INFO: 20% (2.4 GiB of 11.7 GiB) in 42s, read: 61.3 MiB/s, write: 60.0 MiB/s
INFO: 22% (2.6 GiB of 11.7 GiB) in 45s, read: 62.7 MiB/s, write: 58.7 MiB/s
INFO: 23% (2.8 GiB of 11.7 GiB) in 48s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 24% (2.9 GiB of 11.7 GiB) in 51s, read: 57.3 MiB/s, write: 53.3 MiB/s
INFO: 26% (3.1 GiB of 11.7 GiB) in 54s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 27% (3.2 GiB of 11.7 GiB) in 57s, read: 58.7 MiB/s, write: 56.0 MiB/s
INFO: 29% (3.4 GiB of 11.7 GiB) in 1m, read: 58.7 MiB/s, write: 53.3 MiB/s
INFO: 30% (3.6 GiB of 11.7 GiB) in 1m 3s, read: 60.0 MiB/s, write: 54.7 MiB/s
INFO: 32% (3.8 GiB of 11.7 GiB) in 1m 6s, read: 56.0 MiB/s, write: 50.7 MiB/s
INFO: 33% (3.9 GiB of 11.7 GiB) in 1m 9s, read: 57.3 MiB/s, write: 56.0 MiB/s
INFO: 35% (4.1 GiB of 11.7 GiB) in 1m 12s, read: 58.7 MiB/s, write: 53.3 MiB/s
INFO: 36% (4.3 GiB of 11.7 GiB) in 1m 16s, read: 43.0 MiB/s, write: 43.0 MiB/s
INFO: 37% (4.4 GiB of 11.7 GiB) in 1m 19s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 39% (4.6 GiB of 11.7 GiB) in 1m 22s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 40% (4.8 GiB of 11.7 GiB) in 1m 25s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 42% (5.0 GiB of 11.7 GiB) in 1m 28s, read: 68.0 MiB/s, write: 68.0 MiB/s
INFO: 43% (5.1 GiB of 11.7 GiB) in 1m 31s, read: 60.0 MiB/s, write: 60.0 MiB/s
INFO: 45% (5.3 GiB of 11.7 GiB) in 1m 34s, read: 53.3 MiB/s, write: 53.3 MiB/s
INFO: 46% (5.5 GiB of 11.7 GiB) in 1m 37s, read: 57.3 MiB/s, write: 56.0 MiB/s
INFO: 48% (5.6 GiB of 11.7 GiB) in 1m 40s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 49% (5.8 GiB of 11.7 GiB) in 1m 43s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 50% (5.9 GiB of 11.7 GiB) in 1m 46s, read: 52.0 MiB/s, write: 50.7 MiB/s
INFO: 52% (6.1 GiB of 11.7 GiB) in 1m 49s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 53% (6.3 GiB of 11.7 GiB) in 1m 52s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 54% (6.4 GiB of 11.7 GiB) in 1m 55s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 56% (6.6 GiB of 11.7 GiB) in 1m 58s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 57% (6.7 GiB of 11.7 GiB) in 2m 1s, read: 53.3 MiB/s, write: 53.3 MiB/s
INFO: 59% (6.9 GiB of 11.7 GiB) in 2m 4s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 60% (7.1 GiB of 11.7 GiB) in 2m 7s, read: 50.7 MiB/s, write: 50.7 MiB/s
INFO: 61% (7.2 GiB of 11.7 GiB) in 2m 10s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 63% (7.4 GiB of 11.7 GiB) in 2m 13s, read: 57.3 MiB/s, write: 57.3 MiB/s
INFO: 64% (7.6 GiB of 11.7 GiB) in 2m 16s, read: 68.0 MiB/s, write: 62.7 MiB/s
INFO: 66% (7.8 GiB of 11.7 GiB) in 2m 19s, read: 64.0 MiB/s, write: 58.7 MiB/s
INFO: 68% (7.9 GiB of 11.7 GiB) in 2m 22s, read: 60.0 MiB/s, write: 58.7 MiB/s
INFO: 69% (8.1 GiB of 11.7 GiB) in 2m 25s, read: 53.3 MiB/s, write: 52.0 MiB/s
INFO: 70% (8.3 GiB of 11.7 GiB) in 2m 28s, read: 53.3 MiB/s, write: 52.0 MiB/s
INFO: 72% (8.4 GiB of 11.7 GiB) in 2m 31s, read: 53.3 MiB/s, write: 53.3 MiB/s
INFO: 73% (8.6 GiB of 11.7 GiB) in 2m 34s, read: 58.7 MiB/s, write: 54.7 MiB/s
INFO: 74% (8.7 GiB of 11.7 GiB) in 2m 37s, read: 52.0 MiB/s, write: 49.3 MiB/s
INFO: 76% (8.9 GiB of 11.7 GiB) in 2m 40s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 77% (9.1 GiB of 11.7 GiB) in 2m 43s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 79% (9.2 GiB of 11.7 GiB) in 2m 46s, read: 57.3 MiB/s, write: 54.7 MiB/s
INFO: 80% (9.4 GiB of 11.7 GiB) in 2m 49s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 81% (9.5 GiB of 11.7 GiB) in 2m 52s, read: 52.0 MiB/s, write: 52.0 MiB/s
INFO: 83% (9.7 GiB of 11.7 GiB) in 2m 55s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 84% (9.9 GiB of 11.7 GiB) in 2m 58s, read: 52.0 MiB/s, write: 50.7 MiB/s
INFO: 85% (10.0 GiB of 11.7 GiB) in 3m 1s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 87% (10.2 GiB of 11.7 GiB) in 3m 4s, read: 57.3 MiB/s, write: 54.7 MiB/s
INFO: 88% (10.4 GiB of 11.7 GiB) in 3m 7s, read: 57.3 MiB/s, write: 56.0 MiB/s
INFO: 90% (10.5 GiB of 11.7 GiB) in 3m 10s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 91% (10.7 GiB of 11.7 GiB) in 3m 13s, read: 54.7 MiB/s, write: 54.7 MiB/s
INFO: 92% (10.8 GiB of 11.7 GiB) in 3m 16s, read: 50.7 MiB/s, write: 50.7 MiB/s
INFO: 94% (11.0 GiB of 11.7 GiB) in 3m 19s, read: 52.0 MiB/s, write: 52.0 MiB/s
INFO: 95% (11.1 GiB of 11.7 GiB) in 3m 22s, read: 52.0 MiB/s, write: 52.0 MiB/s
INFO: 96% (11.3 GiB of 11.7 GiB) in 3m 25s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 98% (11.5 GiB of 11.7 GiB) in 3m 28s, read: 54.7 MiB/s, write: 54.7 MiB/s
INFO: 99% (11.6 GiB of 11.7 GiB) in 3m 31s, read: 52.0 MiB/s, write: 52.0 MiB/s
INFO: 100% (11.7 GiB of 11.7 GiB) in 3m 34s, read: 25.3 MiB/s, write: 25.3 MiB/s
INFO: Waiting for server to finish backup validation...
INFO: backup was done incrementally, reused 20.69 GiB (64%)
INFO: transferred 11.68 GiB in 225 seconds (53.2 MiB/s)
INFO: adding notes to backup
INFO: Finished Backup of VM 201 (00:03:51)
INFO: Backup finished at 2025-12-02 14:56:21
INFO: Backup job finished successfully
INFO: notified via target `mail-to-root`
TASK OK

 

[pfornara]

those numbers seem fine? note that the bitmap was cleared, so the backup had to read the full disk contents (and did so at roughly 400MB/s!)

yep you're right, but its write speed very strange on a 10Gbit link

 

[GE_Admin]

1 Gbps backup:



INFO: starting new backup job: vzdump 201 --remove 0 --node stige --storage pbs01 --notes-template '{{guestname}}' --notification-mode auto --mode snapshot
INFO: Starting Backup of VM 201 (qemu)
INFO: Backup started at 2025-12-02 14:52:30
INFO: status = running
INFO: VM Name: SMIPRINTER
INFO: include disk 'scsi1' 'local-lvm:vm-201-disk-1' 32G
INFO: include disk 'efidisk0' 'local-lvm:vm-201-disk-0' 4M
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: creating Proxmox Backup Server archive 'vm/201/2025-12-02T13:52:30Z'
INFO: issuing guest-agent 'fs-freeze' command
INFO: issuing guest-agent 'fs-thaw' command
INFO: started backup task 'a5f1509f-cec7-4fed-982c-5a6e83682760'
INFO: resuming VM again
INFO: efidisk0: dirty-bitmap status: OK (drive clean)
INFO: scsi1: dirty-bitmap status: OK (11.7 GiB of 32.0 GiB dirty)
INFO: using fast incremental mode (dirty-bitmap), 11.7 GiB dirty of 32.0 GiB total
INFO: 1% (228.0 MiB of 11.7 GiB) in 3s, read: 76.0 MiB/s, write: 68.0 MiB/s
INFO: 3% (408.0 MiB of 11.7 GiB) in 6s, read: 60.0 MiB/s, write: 52.0 MiB/s
INFO: 4% (572.0 MiB of 11.7 GiB) in 9s, read: 54.7 MiB/s, write: 54.7 MiB/s
INFO: 6% (736.0 MiB of 11.7 GiB) in 12s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 7% (900.0 MiB of 11.7 GiB) in 15s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 8% (1.0 GiB of 11.7 GiB) in 18s, read: 56.0 MiB/s, write: 52.0 MiB/s
INFO: 10% (1.2 GiB of 11.7 GiB) in 21s, read: 53.3 MiB/s, write: 50.7 MiB/s
INFO: 11% (1.4 GiB of 11.7 GiB) in 24s, read: 57.3 MiB/s, write: 57.3 MiB/s
INFO: 13% (1.6 GiB of 11.7 GiB) in 27s, read: 64.0 MiB/s, write: 61.3 MiB/s
INFO: 14% (1.7 GiB of 11.7 GiB) in 30s, read: 60.0 MiB/s, write: 60.0 MiB/s
INFO: 16% (1.9 GiB of 11.7 GiB) in 33s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 17% (2.1 GiB of 11.7 GiB) in 36s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 19% (2.2 GiB of 11.7 GiB) in 39s, read: 57.3 MiB/s, write: 54.7 MiB/s
INFO: 20% (2.4 GiB of 11.7 GiB) in 42s, read: 61.3 MiB/s, write: 60.0 MiB/s
INFO: 22% (2.6 GiB of 11.7 GiB) in 45s, read: 62.7 MiB/s, write: 58.7 MiB/s
INFO: 23% (2.8 GiB of 11.7 GiB) in 48s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 24% (2.9 GiB of 11.7 GiB) in 51s, read: 57.3 MiB/s, write: 53.3 MiB/s
INFO: 26% (3.1 GiB of 11.7 GiB) in 54s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 27% (3.2 GiB of 11.7 GiB) in 57s, read: 58.7 MiB/s, write: 56.0 MiB/s
INFO: 29% (3.4 GiB of 11.7 GiB) in 1m, read: 58.7 MiB/s, write: 53.3 MiB/s
INFO: 30% (3.6 GiB of 11.7 GiB) in 1m 3s, read: 60.0 MiB/s, write: 54.7 MiB/s
INFO: 32% (3.8 GiB of 11.7 GiB) in 1m 6s, read: 56.0 MiB/s, write: 50.7 MiB/s
INFO: 33% (3.9 GiB of 11.7 GiB) in 1m 9s, read: 57.3 MiB/s, write: 56.0 MiB/s
INFO: 35% (4.1 GiB of 11.7 GiB) in 1m 12s, read: 58.7 MiB/s, write: 53.3 MiB/s
INFO: 36% (4.3 GiB of 11.7 GiB) in 1m 16s, read: 43.0 MiB/s, write: 43.0 MiB/s
INFO: 37% (4.4 GiB of 11.7 GiB) in 1m 19s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 39% (4.6 GiB of 11.7 GiB) in 1m 22s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 40% (4.8 GiB of 11.7 GiB) in 1m 25s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 42% (5.0 GiB of 11.7 GiB) in 1m 28s, read: 68.0 MiB/s, write: 68.0 MiB/s
INFO: 43% (5.1 GiB of 11.7 GiB) in 1m 31s, read: 60.0 MiB/s, write: 60.0 MiB/s
INFO: 45% (5.3 GiB of 11.7 GiB) in 1m 34s, read: 53.3 MiB/s, write: 53.3 MiB/s
INFO: 46% (5.5 GiB of 11.7 GiB) in 1m 37s, read: 57.3 MiB/s, write: 56.0 MiB/s
INFO: 48% (5.6 GiB of 11.7 GiB) in 1m 40s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 49% (5.8 GiB of 11.7 GiB) in 1m 43s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 50% (5.9 GiB of 11.7 GiB) in 1m 46s, read: 52.0 MiB/s, write: 50.7 MiB/s
INFO: 52% (6.1 GiB of 11.7 GiB) in 1m 49s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 53% (6.3 GiB of 11.7 GiB) in 1m 52s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 54% (6.4 GiB of 11.7 GiB) in 1m 55s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 56% (6.6 GiB of 11.7 GiB) in 1m 58s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 57% (6.7 GiB of 11.7 GiB) in 2m 1s, read: 53.3 MiB/s, write: 53.3 MiB/s
INFO: 59% (6.9 GiB of 11.7 GiB) in 2m 4s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 60% (7.1 GiB of 11.7 GiB) in 2m 7s, read: 50.7 MiB/s, write: 50.7 MiB/s
INFO: 61% (7.2 GiB of 11.7 GiB) in 2m 10s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 63% (7.4 GiB of 11.7 GiB) in 2m 13s, read: 57.3 MiB/s, write: 57.3 MiB/s
INFO: 64% (7.6 GiB of 11.7 GiB) in 2m 16s, read: 68.0 MiB/s, write: 62.7 MiB/s
INFO: 66% (7.8 GiB of 11.7 GiB) in 2m 19s, read: 64.0 MiB/s, write: 58.7 MiB/s
INFO: 68% (7.9 GiB of 11.7 GiB) in 2m 22s, read: 60.0 MiB/s, write: 58.7 MiB/s
INFO: 69% (8.1 GiB of 11.7 GiB) in 2m 25s, read: 53.3 MiB/s, write: 52.0 MiB/s
INFO: 70% (8.3 GiB of 11.7 GiB) in 2m 28s, read: 53.3 MiB/s, write: 52.0 MiB/s
INFO: 72% (8.4 GiB of 11.7 GiB) in 2m 31s, read: 53.3 MiB/s, write: 53.3 MiB/s
INFO: 73% (8.6 GiB of 11.7 GiB) in 2m 34s, read: 58.7 MiB/s, write: 54.7 MiB/s
INFO: 74% (8.7 GiB of 11.7 GiB) in 2m 37s, read: 52.0 MiB/s, write: 49.3 MiB/s
INFO: 76% (8.9 GiB of 11.7 GiB) in 2m 40s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 77% (9.1 GiB of 11.7 GiB) in 2m 43s, read: 56.0 MiB/s, write: 54.7 MiB/s
INFO: 79% (9.2 GiB of 11.7 GiB) in 2m 46s, read: 57.3 MiB/s, write: 54.7 MiB/s
INFO: 80% (9.4 GiB of 11.7 GiB) in 2m 49s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 81% (9.5 GiB of 11.7 GiB) in 2m 52s, read: 52.0 MiB/s, write: 52.0 MiB/s
INFO: 83% (9.7 GiB of 11.7 GiB) in 2m 55s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 84% (9.9 GiB of 11.7 GiB) in 2m 58s, read: 52.0 MiB/s, write: 50.7 MiB/s
INFO: 85% (10.0 GiB of 11.7 GiB) in 3m 1s, read: 56.0 MiB/s, write: 56.0 MiB/s
INFO: 87% (10.2 GiB of 11.7 GiB) in 3m 4s, read: 57.3 MiB/s, write: 54.7 MiB/s
INFO: 88% (10.4 GiB of 11.7 GiB) in 3m 7s, read: 57.3 MiB/s, write: 56.0 MiB/s
INFO: 90% (10.5 GiB of 11.7 GiB) in 3m 10s, read: 54.7 MiB/s, write: 53.3 MiB/s
INFO: 91% (10.7 GiB of 11.7 GiB) in 3m 13s, read: 54.7 MiB/s, write: 54.7 MiB/s
INFO: 92% (10.8 GiB of 11.7 GiB) in 3m 16s, read: 50.7 MiB/s, write: 50.7 MiB/s
INFO: 94% (11.0 GiB of 11.7 GiB) in 3m 19s, read: 52.0 MiB/s, write: 52.0 MiB/s
INFO: 95% (11.1 GiB of 11.7 GiB) in 3m 22s, read: 52.0 MiB/s, write: 52.0 MiB/s
INFO: 96% (11.3 GiB of 11.7 GiB) in 3m 25s, read: 54.7 MiB/s, write: 52.0 MiB/s
INFO: 98% (11.5 GiB of 11.7 GiB) in 3m 28s, read: 54.7 MiB/s, write: 54.7 MiB/s
INFO: 99% (11.6 GiB of 11.7 GiB) in 3m 31s, read: 52.0 MiB/s, write: 52.0 MiB/s
INFO: 100% (11.7 GiB of 11.7 GiB) in 3m 34s, read: 25.3 MiB/s, write: 25.3 MiB/s
INFO: Waiting for server to finish backup validation...
INFO: backup was done incrementally, reused 20.69 GiB (64%)
INFO: transferred 11.68 GiB in 225 seconds (53.2 MiB/s)
INFO: adding notes to backup
INFO: Finished Backup of VM 201 (00:03:51)
INFO: Backup finished at 2025-12-02 14:56:21
INFO: Backup job finished successfully
INFO: notified via target `mail-to-root`
TASK OK

Slow but constant... Is this test done with the latest kernel, right?

 

[pfornara]

Slow but constant... Is this test done with the latest kernel, right?

nope ... with 6.14

 

[GE_Admin]

nope ... with 6.14

Okay,
I've done a test with latest kernel and 2 x 1 Gbps LACP, 1500 MTU, no VLan and it's working!!!

INFO: starting new backup job: vzdump 110 --node pve-gom-003 --mode snapshot --remove 0 --storage pbs-gom-001_man --notes-template '{{guestname}}' --notification-mode auto
INFO: Starting Backup of VM 110 (qemu)
INFO: Backup started at 2025-12-02 15:43:22
INFO: status = running
INFO: VM Name: SRV-TEST
INFO: include disk 'scsi0' 'Pool_1:vm-110-disk-0' 66112M
INFO: include disk 'scsi1' 'Pool_1:vm-110-disk-1' 262400M
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: creating Proxmox Backup Server archive 'vm/110/2025-12-02T14:43:22Z'
INFO: issuing guest-agent 'fs-freeze' command
INFO: issuing guest-agent 'fs-thaw' command
INFO: started backup task '73eec0a9-f33e-48cc-b86d-c0a7a79df42d'
INFO: resuming VM again
INFO: scsi0: dirty-bitmap status: OK (9.0 GiB of 64.6 GiB dirty)
INFO: scsi1: dirty-bitmap status: OK (1.8 GiB of 256.2 GiB dirty)
INFO: using fast incremental mode (dirty-bitmap), 10.8 GiB dirty of 320.8 GiB total
INFO: 11% (1.2 GiB of 10.8 GiB) in 3s, read: 405.3 MiB/s, write: 361.3 MiB/s
INFO: 19% (2.1 GiB of 10.8 GiB) in 6s, read: 296.0 MiB/s, write: 269.3 MiB/s
INFO: 24% (2.7 GiB of 10.8 GiB) in 9s, read: 214.7 MiB/s, write: 204.0 MiB/s
INFO: 32% (3.5 GiB of 10.8 GiB) in 12s, read: 276.0 MiB/s, write: 261.3 MiB/s
INFO: 39% (4.2 GiB of 10.8 GiB) in 15s, read: 249.3 MiB/s, write: 234.7 MiB/s
INFO: 45% (4.9 GiB of 10.8 GiB) in 18s, read: 221.3 MiB/s, write: 205.3 MiB/s
INFO: 51% (5.6 GiB of 10.8 GiB) in 21s, read: 237.3 MiB/s, write: 232.0 MiB/s
INFO: 57% (6.2 GiB of 10.8 GiB) in 24s, read: 216.0 MiB/s, write: 210.7 MiB/s
INFO: 63% (6.9 GiB of 10.8 GiB) in 27s, read: 224.0 MiB/s, write: 214.7 MiB/s
INFO: 69% (7.5 GiB of 10.8 GiB) in 30s, read: 226.7 MiB/s, write: 218.7 MiB/s
INFO: 77% (8.3 GiB of 10.8 GiB) in 33s, read: 272.0 MiB/s, write: 252.0 MiB/s
INFO: 84% (9.1 GiB of 10.8 GiB) in 36s, read: 272.0 MiB/s, write: 248.0 MiB/s
INFO: 93% (10.1 GiB of 10.8 GiB) in 39s, read: 342.7 MiB/s, write: 244.0 MiB/s
INFO: 100% (10.8 GiB of 10.8 GiB) in 42s, read: 226.7 MiB/s, write: 169.3 MiB/s
INFO: Waiting for server to finish backup validation...
INFO: backup is sparse: 384.00 MiB (3%) total zero data
INFO: backup was done incrementally, reused 311.07 GiB (96%)
INFO: transferred 10.78 GiB in 45 seconds (245.3 MiB/s)
INFO: adding notes to backup
INFO: Finished Backup of VM 110 (00:00:48)
INFO: Backup finished at 2025-12-02 15:44:10
INFO: Backup job finished successfully
INFO: skipping disabled matcher 'default-matcher'
TASK OK

So, on my PBS, the problem arise only on 2 x 10 Gbps LACP, MTU 9000 and MLAG switches... On Gigabit network is working fine.

 

[fiona]

Yet another reminder: people with the issue who do not use ZFS, if you can find the opportunity, please test with mainline kernel builds. As long as we do not have a reproducer for the issue, all we can do is search for kernel commits that seem suspicious. But you could help us a lot to narrow it down by testing:

The ZFS kernel module is the same version 2.3.4+pve1 in both kernel 6.14 and 6.17, so the likely cause of the issue is in the rest of the kernel code. Unfortunately, the difference between 6.14 and 6.17 is very big. If anybody is not using ZFS and still affected by the issue at hand, you could test mainline builds to help narrow it down:
https://kernel.ubuntu.com/mainline/v6.15/
https://kernel.ubuntu.com/mainline/v6.16/
(the amd64/linux-image... and amd64/linux-modules... packages need to be installed).

Testing with the following would also be appreciated, the issue might very well be already fixed in a newer release:
https://kernel.ubuntu.com/mainline/v6.17.10/
https://kernel.ubuntu.com/mainline/v6.18/