Date: Thu, 03 Apr 2025 15:21:55 +0000 From: "Lev Serebryakov" <lev@freebsd.org> To: freebsd-fs@freebsd.org Subject: gptzfsboot cannot boot from ZFS (mirror) with "can't read MOS of pool znewroot" (FreeBSD 13.5-STABLE) Message-ID: <06002a1719b8460c9ac725fae2f2cd756ca05dcd@freebsd.org>
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Hello!
I have ZFS mirror built from two GPT partitions on two SATA drives. It is only ZFS pool on the system, and it looks completely healthy:
% zpool status
pool: znewroot
state: ONLINE
scan: resilvered 784G in 02:05:09 with 0 errors on Wed Jan 8 20:46:14 2025
config:
NAME STATE READ WRITE CKSUM
znewroot ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
gpt/zfs0 ONLINE 0 0 0
gpt/zfs1 ONLINE 0 0 0
errors: No known data errors
Disks are paritioned identically:
% gpart show
=> 40 3907029088 ada1 GPT (1.8T)
40 984 - free - (492K)
1024 1024 1 freebsd-boot (512K)
2048 2097152 2 freebsd-ufs (1.0G)
2099200 65177600 3 freebsd-swap (31G)
67276800 3839750144 4 freebsd-zfs (1.8T)
3907026944 2184 - free - (1.1M)
=> 40 3907029088 ada0 GPT (1.8T)
40 984 - free - (492K)
1024 1024 1 freebsd-boot (512K)
2048 2097152 2 freebsd-ufs (1.0G)
2099200 65177600 3 freebsd-swap (31G)
67276800 3839750144 4 freebsd-zfs (1.8T)
3907026944 2184 - free - (1.1M)
When I try to use `gptzfsboot`, like `gpart -b pmbr -p /boot/gptzfsboot -i 1 ada0 && gpart -b pmbr -p /boot/gptzfsboot -i 1 ada` boot says:
ZFS: i/o error - all block copies unavailable
ZFS: can't read MOS of pool znewroot
As a hack I'm using `gtpboot` & small `freebsd-ufs` partiton with only `/boot` directory.
But I hate this hack, as system update becomes cumbersome, and I cannot convert this system to UEFI boot (because `loader.efi` "Failed to find bootable partition").
What is wrong with my ZFS pool and how could I fix it?
--
// Lev Serebryakov
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