Here is the portion of the log covering the affected VM. Fleece was pointed at the first of two LVM-Thin volumes. Storage is SSD mirror on top of hardware Dell raid controller. I cannot remember what filesystem I chose, but it was not ZFS.
INFO: Starting Backup of VM 106 (qemu)
INFO: Backup started at 2024-05-08 07:54:12
INFO: status = running
INFO: VM Name: GCRFS02
INFO: include disk 'scsi1' 'local-lvm:vm-106-disk-1' 200G
INFO: include disk 'scsi2' 'SATA:vm-106-disk-2' 3584G
INFO: include disk 'scsi3' 'SATA:vm-106-disk-3' 500G
INFO: include disk 'efidisk0' 'local-lvm:vm-106-disk-0' 4M
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: skip unused drive 'SATA:vm-106-disk-0' (not included into backup)
INFO: creating Proxmox Backup Server archive 'vm/106/2024-05-08T11:54:12Z'
WARNING: You have not turned on protection against thin pools running out of space.
WARNING: Set activation/thin_pool_autoextend_threshold below 100 to trigger automatic extension of thin pools before they get full.
Logical volume "vm-106-fleece-0" created.
WARNING: Sum of all thin volume sizes (<2.89 TiB) exceeds the size of thin pool pve/data and the size of whole volume group (1.86 TiB).
WARNING: You have not turned on protection against thin pools running out of space.
WARNING: Set activation/thin_pool_autoextend_threshold below 100 to trigger automatic extension of thin pools before they get full.
Logical volume "vm-106-fleece-1" created.
WARNING: Sum of all thin volume sizes (<6.39 TiB) exceeds the size of thin pool pve/data and the size of whole volume group (1.86 TiB).
WARNING: You have not turned on protection against thin pools running out of space.
WARNING: Set activation/thin_pool_autoextend_threshold below 100 to trigger automatic extension of thin pools before they get full.
Logical volume "vm-106-fleece-2" created.
WARNING: Sum of all thin volume sizes (<6.88 TiB) exceeds the size of thin pool pve/data and the size of whole volume group (1.86 TiB).
INFO: drive-scsi1: attaching fleecing image local-lvm:vm-106-fleece-0 to QEMU
INFO: drive-scsi2: attaching fleecing image local-lvm:vm-106-fleece-1 to QEMU
INFO: drive-scsi3: attaching fleecing image local-lvm:vm-106-fleece-2 to QEMU
INFO: issuing guest-agent 'fs-freeze' command
INFO: issuing guest-agent 'fs-thaw' command
INFO: started backup task '2196b3b6-1279-452d-be59-4d77df1a6bf8'
INFO: resuming VM again
INFO: efidisk0: dirty-bitmap status: created new
INFO: scsi1: dirty-bitmap status: created new
INFO: scsi2: dirty-bitmap status: created new
INFO: scsi3: dirty-bitmap status: created new
INFO: 0% (3.7 GiB of 4.2 TiB) in 3s, read: 1.2 GiB/s, write: 32.0 MiB/s
INFO: 1% (43.0 GiB of 4.2 TiB) in 41s, read: 1.0 GiB/s, write: 538.9 KiB/s
INFO: 2% (86.9 GiB of 4.2 TiB) in 1m 16s, read: 1.3 GiB/s, write: 3.2 MiB/s
INFO: 3% (129.3 GiB of 4.2 TiB) in 1m 52s, read: 1.2 GiB/s, write: 4.3 MiB/s
INFO: 4% (172.8 GiB of 4.2 TiB) in 2m 27s, read: 1.2 GiB/s, write: 4.9 MiB/s
INFO: 5% (214.9 GiB of 4.2 TiB) in 3m 2s, read: 1.2 GiB/s, write: 4.8 MiB/s
INFO: 6% (257.3 GiB of 4.2 TiB) in 3m 39s, read: 1.1 GiB/s, write: 4.6 MiB/s
INFO: 7% (300.7 GiB of 4.2 TiB) in 4m 17s, read: 1.1 GiB/s, write: 4.5 MiB/s
INFO: 8% (343.5 GiB of 4.2 TiB) in 4m 53s, read: 1.2 GiB/s, write: 4.8 MiB/s
INFO: 9% (386.6 GiB of 4.2 TiB) in 5m 30s, read: 1.2 GiB/s, write: 4.6 MiB/s
INFO: 10% (429.1 GiB of 4.2 TiB) in 6m 8s, read: 1.1 GiB/s, write: 4.5 MiB/s
INFO: 11% (472.1 GiB of 4.2 TiB) in 6m 44s, read: 1.2 GiB/s, write: 4.7 MiB/s
INFO: 12% (514.1 GiB of 4.2 TiB) in 12m 15s, read: 129.9 MiB/s, write: 43.1 MiB/s
INFO: 13% (556.9 GiB of 4.2 TiB) in 26m 22s, read: 51.8 MiB/s, write: 51.4 MiB/s
INFO: 14% (599.8 GiB of 4.2 TiB) in 39m 13s, read: 56.9 MiB/s, write: 56.7 MiB/s
INFO: 15% (642.6 GiB of 4.2 TiB) in 52m 32s, read: 54.9 MiB/s, write: 54.8 MiB/s
INFO: 16% (685.5 GiB of 4.2 TiB) in 1h 6m 15s, read: 53.3 MiB/s, write: 53.3 MiB/s
INFO: 17% (728.3 GiB of 4.2 TiB) in 1h 20m 47s, read: 50.3 MiB/s, write: 50.2 MiB/s
INFO: 18% (771.2 GiB of 4.2 TiB) in 1h 36m 6s, read: 47.8 MiB/s, write: 47.2 MiB/s
INFO: 19% (814.0 GiB of 4.2 TiB) in 1h 50m 43s, read: 50.1 MiB/s, write: 49.6 MiB/s
INFO: 20% (856.8 GiB of 4.2 TiB) in 2h 3m 58s, read: 55.1 MiB/s, write: 53.7 MiB/s
INFO: 21% (899.7 GiB of 4.2 TiB) in 2h 18m 39s, read: 49.8 MiB/s, write: 48.1 MiB/s
INFO: 22% (942.5 GiB of 4.2 TiB) in 2h 34m 57s, read: 44.8 MiB/s, write: 44.1 MiB/s
INFO: 23% (985.4 GiB of 4.2 TiB) in 2h 50m 55s, read: 45.8 MiB/s, write: 45.4 MiB/s
INFO: 24% (1.0 TiB of 4.2 TiB) in 3h 6m 44s, read: 46.2 MiB/s, write: 45.5 MiB/s
INFO: 25% (1.0 TiB of 4.2 TiB) in 3h 20m 50s, read: 51.9 MiB/s, write: 51.6 MiB/s
INFO: 26% (1.1 TiB of 4.2 TiB) in 3h 35m 40s, read: 49.3 MiB/s, write: 48.9 MiB/s
INFO: 27% (1.1 TiB of 4.2 TiB) in 3h 49m 53s, read: 51.4 MiB/s, write: 51.1 MiB/s
INFO: 28% (1.2 TiB of 4.2 TiB) in 4h 4m 42s, read: 49.4 MiB/s, write: 49.1 MiB/s
INFO: 29% (1.2 TiB of 4.2 TiB) in 4h 17m 53s, read: 55.5 MiB/s, write: 55.4 MiB/s
INFO: 30% (1.3 TiB of 4.2 TiB) in 4h 32m 59s, read: 48.4 MiB/s, write: 48.0 MiB/s
INFO: 31% (1.3 TiB of 4.2 TiB) in 4h 47m 37s, read: 50.0 MiB/s, write: 49.8 MiB/s
INFO: 32% (1.3 TiB of 4.2 TiB) in 5h 1m 32s, read: 52.5 MiB/s, write: 52.4 MiB/s
INFO: 33% (1.4 TiB of 4.2 TiB) in 5h 16m 26s, read: 49.1 MiB/s, write: 48.7 MiB/s
INFO: 34% (1.4 TiB of 4.2 TiB) in 5h 32m 20s, read: 46.0 MiB/s, write: 45.9 MiB/s
INFO: 35% (1.5 TiB of 4.2 TiB) in 5h 50m 53s, read: 39.4 MiB/s, write: 39.1 MiB/s
INFO: 36% (1.5 TiB of 4.2 TiB) in 6h 10m 37s, read: 37.1 MiB/s, write: 37.0 MiB/s
INFO: 37% (1.5 TiB of 4.2 TiB) in 6h 31m 37s, read: 34.8 MiB/s, write: 34.8 MiB/s
INFO: 38% (1.6 TiB of 4.2 TiB) in 6h 53m 16s, read: 33.8 MiB/s, write: 33.7 MiB/s
INFO: 39% (1.6 TiB of 4.2 TiB) in 7h 14m 49s, read: 33.9 MiB/s, write: 33.9 MiB/s
INFO: 40% (1.7 TiB of 4.2 TiB) in 7h 37m 28s, read: 32.3 MiB/s, write: 32.1 MiB/s
INFO: 41% (1.7 TiB of 4.2 TiB) in 8h 1m 41s, read: 30.2 MiB/s, write: 30.1 MiB/s
INFO: 42% (1.8 TiB of 4.2 TiB) in 8h 23m 49s, read: 33.0 MiB/s, write: 33.0 MiB/s
INFO: 43% (1.8 TiB of 4.2 TiB) in 8h 46m 59s, read: 31.6 MiB/s, write: 30.7 MiB/s
INFO: 44% (1.8 TiB of 4.2 TiB) in 9h 11m 29s, read: 29.8 MiB/s, write: 29.7 MiB/s
INFO: 45% (1.9 TiB of 4.2 TiB) in 9h 34m 55s, read: 31.2 MiB/s, write: 30.9 MiB/s
INFO: 46% (1.9 TiB of 4.2 TiB) in 9h 58m 49s, read: 30.6 MiB/s, write: 30.5 MiB/s
INFO: 47% (2.0 TiB of 4.2 TiB) in 10h 24m 12s, read: 28.8 MiB/s, write: 28.8 MiB/s
INFO: 48% (2.0 TiB of 4.2 TiB) in 10h 49m 15s, read: 29.2 MiB/s, write: 28.7 MiB/s
INFO: 49% (2.0 TiB of 4.2 TiB) in 11h 13m 7s, read: 30.7 MiB/s, write: 30.5 MiB/s
INFO: 50% (2.1 TiB of 4.2 TiB) in 11h 38m 6s, read: 29.3 MiB/s, write: 29.1 MiB/s
INFO: 51% (2.1 TiB of 4.2 TiB) in 12h 4m 18s, read: 27.9 MiB/s, write: 27.7 MiB/s
INFO: 52% (2.2 TiB of 4.2 TiB) in 12h 28m 17s, read: 30.5 MiB/s, write: 30.1 MiB/s
INFO: 53% (2.2 TiB of 4.2 TiB) in 12h 51m 10s, read: 32.0 MiB/s, write: 31.2 MiB/s
ERROR: interrupted by signal
INFO: aborting backup job
INFO: resuming VM again
