weird bug with ZFS and SLOG

[Adam Stylinski]

On Tue, Dec 6, 2011 at 5:07 AM, Volodymyr Kostyrko <c.kworr at gmail.com>wrote:

> 06.12.2011 00:07, Adam Stylinski wrote:
>
>> The worst case scenario happened to me where my dedicated SLOG decided to
>> drop off the controller and thus prevent me from importing my pool.  I
>> quickly upgrade to FreeBSD 9.0-RC2 after testing this scenario in a VM.  It
>> has worked successfully in a VM, but it is not working on my hardware for
>> whatever reason.  I rollback the pool with zpool import -F share, seems ok,
>> files are there, finishes scrub, very little corruption.  I upgrade the
>> pool to V28, and the fs's to v5.  I then do a:
>>         zpool remove share 15752248745115926170
>>
>>        It returns no errors and pretends like the operation worked, it
>> even appends it to my zpool history.  However, when I do a zpool status,
>> this is what I get:
>>
>
> Just a +1 from me, I have such pool also:
>
>  pool: utwig
>  state: DEGRADED
> status: One or more devices has been taken offline by the administrator.
>        Sufficient replicas exist for the pool to continue functioning in a
>        degraded state.
> action: Online the device using 'zpool online' or replace the device with
>        'zpool replace'.
>  scan: resilvered 73,6M in 0h0m with 0 errors on Fri Oct 28 14:37:10 2011
>
> config:
>
>        NAME                                            STATE     READ
> WRITE CKSUM
>        utwig                                           DEGRADED     0
> 0     0
>          mirror-0                                      ONLINE       0
> 0     0
>            gptid/ecb17af1-9119-11df-bb0b-**00304f4e6d80  ONLINE       0
>   0     0
>            gptid/03aed1f5-95a3-11df-bb0b-**00304f4e6d80  ONLINE       0
>   0     0
>        logs
>          gptid/231b9002-a4a5-11e0-a114-**3f386a87752c    OFFLINE      0
>   0     0
>
> As you see I just 'offline'd that device.
>
> Common points:
> 1. Pool was created on 8.x.
> 2. Machine runs 8_STABLE now, pool was upgraded after log device fails to
> detach.
>
> Other hints:
> The log device can be substituted with other device yet it cannot be
> deleted anyway. If you have some spare place on the disk to create some
> small partition for log and replace missed device with such partition.
>
>
>  What is going on here and how do I fix it?
>>
>
> Dunno why but the pool now _requires_ log device. While log device is not
> present pool should use an on-disk log and everything-should-work-fine TM.
>
> --
> Sphinx of black quartz judge my vow.
>

Actually my pool was created on 7.2 and has been updated every release, is
that a factor?  I did manage to do this in a VM, so in any case we'll
probably have to do something that involves zdb.