Solved Can't read MOS of pool zroot

circus78

Active Member

Reaction score: 7
Messages: 224

Hi, yesterday I restarted one of my server and I was unable to boot.
The error I got is:

Code:
ZFS: i/o error - all block copies unavailable
ZFS: can't read MOS of pool zroot
gptzfsboot: failed to mount default pool zroot
System is FreeBSD 11.2 with 4 x 3 TB SATA disks (all disks led are green - OK).
I am pretty sure I used raidz1 level.
How can I troubleshoot this?

Thank you
 
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circus78

Active Member

Reaction score: 7
Messages: 224

Hi, I have been able to access data on filesystem through FreeBSD live cd.
Apparently it seems all fine:

Code:
root@:~ # zpool status
  pool: zroot
 state: ONLINE
  scan: resilvered 773G in 100h11m with 0 errors on Sun May 12 19:38:11 2019
config:

        NAME          STATE     READ WRITE CKSUM
        zroot         ONLINE       0     0     0
          raidz1-0    ONLINE       0     0     0
            gpt/zfs0  ONLINE       0     0     0
            da0p3     ONLINE       0     0     0
            da1p3     ONLINE       0     0     0
            da2p3     ONLINE       0     0     0

errors: No known data errors
root@:~ #
Code:
root@:~ # zfs list
NAME                 USED  AVAIL  REFER  MOUNTPOINT
zroot               2.29T  1.54T   140K  /tmp/mydata/zroot
zroot/ROOT          1.85T  1.54T   140K  none
zroot/ROOT/default  1.85T  1.54T  1.85T  /tmp/mydata
zroot/tmp            215K  1.54T   215K  /tmp/mydata/tmp
zroot/usr            444G  1.54T   140K  /tmp/mydata/usr
zroot/usr/home       442G  1.54T   442G  /tmp/mydata/usr/home
zroot/usr/ports     1.97G  1.54T  1.97G  /tmp/mydata/usr/ports
zroot/usr/src        140K  1.54T   140K  /tmp/mydata/usr/src
zroot/var           1.79M  1.54T   140K  /tmp/mydata/var
zroot/var/audit      140K  1.54T   140K  /tmp/mydata/var/audit
zroot/var/crash      140K  1.54T   140K  /tmp/mydata/var/crash
zroot/var/log       1.08M  1.54T  1.08M  /tmp/mydata/var/log
zroot/var/mail       174K  1.54T   174K  /tmp/mydata/var/mail
zroot/var/tmp        140K  1.54T   140K  /tmp/mydata/var/tmp
root@:~ #
I am trying to figure why I had such issue during boot. Any suggestion?
Thank you very much
 

ralphbsz

Daemon

Reaction score: 1,163
Messages: 1,871

Any suggestion? No idea. Clearly, when you booted and got that error message, none of the four disks were available to the kernel. And then when you booted the second time from a live CD, all four were available. I have no idea what changed in the meantime. If the problem reoccurs, try this: boot, and stop the machine in the BIOS menu. Go into the BIOS configuration or setup menu, and find out what drives it sees as connected. If it sees all 4, or if it sees zero, you know that the problem is pervasive.

Educated guess: Bad connectors or loose wiring, although it is a bit strange that it owuld affect all 4 disks, while the disk lights are on. But in general, reseating connectors solves 90% of all problems with amateur-grade machines.
 
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circus78

Active Member

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Messages: 224

Hi ralphbsz,
you were absolutely right. After reboot, all went ok.
I can't fully understand your theory, anyway: if all drives were unavailable, how do you explain the error I got (originated from zfs)?
It wasn't an error from BIOS or hardware controller.

Thank you again :)
 
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