seems not related to 285 drivers.
downgrade to 271 for safety.
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Hangs / services crash can occur during backup if destination is too slow.
FYI, initial bugs was after 208 and before 266 virtio drivers, fixed late 2024.
Here add -global scsi-hd.discard_granularity=8M to args:
8M because with 2M Windows 10 v1809 / Server 2019 doesn't report "SLAB" size.
Not yet tried with PVE v9
Systemd-boot is installed with UEFI Not Enabled Secure Boot with ZFS/BTRFS.
GRUB bootloader is installed when Secure Boot is enabled in UEFI, even with ZFS or BTRFS.