misc/159045: ZFS scrub freezes system

[Vladislav V. Prodan]

>Number:         159045
>Category:       misc
>Synopsis:       ZFS scrub freezes system
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jul 19 21:40:08 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Vladislav V. Prodan
>Release:        FreeBSD 8.2-STABLE amd64
>Organization:
>Environment:
FreeBSD mary-teresa.XXXXX.ua 8.2-STABLE FreeBSD 8.2-STABLE #0: Wed Jul 13 02:01:02 EEST 2011     root at mary-teresa.XXXXX.ua:/usr/obj/usr/src/sys/XXXXX.4  amd64

>Description:
# zpool list
NAME      SIZE  ALLOC   FREE    CAP  DEDUP  HEALTH  ALTROOT
tank     4,06T  2,82T  1,24T    69%  1.00x  DEGRADED  -
zbackup   464G   181G   283G    39%  1.00x  ONLINE  -
zroot     460G  90,7G   369G    19%  1.06x  ONLINE  -
# zpool upgrade
This system is currently running ZFS pool version 28.

All pools are formatted using this version.
# zfs upgrade
This system is currently running ZFS filesystem version 5.

All filesystems are formatted with the current version.


I ran
# zfs scrub zbackup
then the system froze.
Ping to the server running, but the other services - web, nat, mail - did not respond.

After a hard reboot check this pool continued independently:
# zpool status zbackup
  pool: zbackup
 state: ONLINE
 scan: scrub in progress since Wed Jul 20 00:14:36 2011
    26,9G scanned out of 181G at 1/s, (scan is slow, no estimated time)
    0 repaired, 14,82% done
config:

        NAME               STATE     READ WRITE CKSUM
        zbackup            ONLINE       0     0     0
          gpt/disk-backup  ONLINE       0     0     0

errors: No known data errors

>How-To-Repeat:
zfs scrub <pool>
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: