[zfs-discuss] zfs-discuss Digest, Vol 7, Issue 59

hunter morgan automaticgiant at gmail.com
Thu Jan 7 04:24:44 EST 2016

>  Here is the thing: cache devices are *not* listed in the vdev tree.
Why is that? I want sauce for that claim, due, in part, to output I'll
provide shortly.

> Your zdb output here says that your pool is supposed to have two vdevs
> ('vdev_children:2') and you can find one (the raidz vdev).  However, the
> second child vdev, id 1 and type 'missing', is not there; the 'missing'
> type is a special vdev type that ZFS fills in when the pool data says
> there should be a child vdev but it can't be found.
Idk why zdb says that or which os it was from, but zpool import
doesn't give quite the same information. I guess I'd have to look
through the nvlists to really understand what it was referring to, but
zfs-on-linux 0.6.5-pve6~jessi (proxmox) says:

root:~# zpool import
   pool: pool5
     id: 14850262647910895720
  state: UNAVAIL
 status: The pool was last accessed by another system.
 action: The pool cannot be imported due to damaged devices or data.
   see: http://zfsonlinux.org/msg/ZFS-8000-EY

        pool5        UNAVAIL  missing device
          raidz2-0   ONLINE
            sde      ONLINE
            sdf      ONLINE
            sdd      ONLINE
            sdg      ONLINE
            sdc      ONLINE

and freebsd 10.2 says:
(sameish but can't copy/paste because it's in a kvm console)
raidz2-0 online
disk online
disk online
disk online
disk online
disk online

instead of missing, so it seems like it's looking for a cache disk
with that guid.

I haven't quite gotten around to tracing the import through user and
kernelspace to find the exact error path, but I did replace the guid
of a new cache disk with this one in all 4 copies of the vdev label.
with the same results. I think I'm going to try and grok the nvlists
on that cache disk to see if a vdev tree is present that I need to
modify and/or grok the original pool5 vdev tree.

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