Snapshots don't work for me.
in logs after a successful backup;
2019-12-23 12:51 information: commited changes from snapshot for /mnt/user/domains/Linux/vdisk1.img on Linux.
2019-12-23 12:52 information: forcibly removed snapshot /mnt/user/domains/Linux/vdisk1.snap for Linux.
Backups successful, check attached device is still called snap;
# virsh domblklist 6
Target Source
-----------------------------------------------
hdc /mnt/user/domains/Linux/vdisk1.snap
Looks like this.
# ls -la
total 13294048
drwxrwxrwx 1 nobody users 76 Dec 23 12:52 ./
drwxrwxrwx 1 nobody users 26 Dec 23 12:04 ../
-rw------- 1 root users 1441792 Dec 23 12:52 .fuse_hidden0002bcca0000044a
-rwxrwxrwx 1 root users 17179869184 Dec 23 12:46 vdisk1.img*
If you then stop the vm, and try to start it, it will fail as the .snap file doesn't exist. If you rename it to .img it's been rolled back to the pre-backup state.
Additionally the extensions to skip is case sensitive, I suspect this is not the intention as there is some setopts -u nocasematch in the code;
I had install media attached to a windows vm; after the above backup it left the .ISO attached device as a .snap too.
2019-12-23 12:15 information: able to perform snapshot for disk /mnt/user/recovery/Operating System ISO/9200.16384.WIN8_RTM.120725-1247_X64FRE_SERVER_EVAL_EN-US-HRM_SSS_X64FREE_EN-US_DV5.ISO on WinPrint. use_snapshots is 1. vm_state is running. vdisk_type is raw
2019-12-23 12:15 information: qemu agent found. enabling quiesce on snapshot.
2019-12-23 12:15 failure: snapshot command failed on 9200.16384.WIN8_RTM.120725-1247_X64FRE_SERVER_EVAL_EN-US-HRM_SSS_X64FREE_EN-US_DV5.snap for WinPrint.
2019-12-23 12:15 failure: snapshot_fallback is 0. skipping backup for WinPrint to prevent data loss. no cleanup will be performed for this vm.
running unraid 6.7.2