# ZFS + NFS hang during nightly jobs



## cjyar (Jan 4, 2014)

I'm seeing a hang in ZFS-related processes, occasionally when various nighttime jobs are running. This is on 9.2-RELEASE/amd64. I have two ZFS pools. The maxwell pool is exporting one NFS filesystem; the paydirt filesystem doesn't export anything.


```
pool: maxwell
 state: ONLINE
  scan: scrub repaired 0 in 0h49m with 0 errors on Mon Dec  2 04:01:04 2013
config:

        NAME          STATE     READ WRITE CKSUM
        maxwell       ONLINE       0     0     0
          mirror-0    ONLINE       0     0     0
            gpt/max1  ONLINE       0     0     0
            gpt/max0  ONLINE       0     0     0

errors: No known data errors

  pool: paydirt
 state: ONLINE
status: One or more devices are faulted in response to IO failures.
action: Make sure the affected devices are connected, then run 'zpool clear'.
   see: http://illumos.org/msg/ZFS-8000-HC
  scan: scrub repaired 0 in 2h8m with 0 errors on Tue Dec 24 05:21:06 2013
config:

        NAME              STATE     READ WRITE CKSUM
        paydirt           ONLINE       2     0     0
          mirror-0        ONLINE      10     0     0
            gpt/paydirt2  ONLINE       4     0     0
            gpt/paydirt1  ONLINE       2     0     0

errors: 2 data errors, use '-v' for a list
```

Here's what ps shows me for the three hung processes:

```
UID  PID PPID CPU PRI NI   VSZ  RSS MWCHAN   STAT TT     TIME COMMAND
  0 5626 5624   0  52  0 37624 2508 db->db_c D    ??  0:00.01 zfs list -H
  0 816    1   0  20  0 12080 1276 zio->io_ Ds   ??  0:00.48 /usr/sbin/mountd -r /etc/exports /etc/zfs/exports
65534 93232 93224   0  52  5 9944 2860 db->db_c DN   ??  0:00.28 find -s / ! ( -fstype ufs -or -fstype zfs ) -prune -or -path /tmp -prune -or -path /usr/tmp -prune -or -path /var/tmp -prune -or -path /var/db/portsnap -prune -or -name .zfs -type d -prune -or -print
```


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