[zfs-discuss] Removing log device from existing pool

Durval Menezes durval.menezes at gmail.com
Fri Dec 8 07:03:56 EST 2017


Hello Uwe,

On Fri, Dec 8, 2017 at 9:48 AM, Uwe Sauter via zfs-discuss <
zfs-discuss at list.zfsonlinux.org> wrote:

> Could you be a bit more specific (commands and output)?


Not sure whether you are talking to Marco or to me, but I've included
everything in the github issue I mentioned in my last message (again:
https://github.com/zfsonlinux/zfs/issues/6677) .



> The man page states:
>
>      Log devices can be added, replaced, attached, detached, and imported
> and exported as part of the
>      larger pool.  Mirrored log devices can be removed by specifying the
> top-level mirror for the log.
>

Interesting. Not sure about what man page you're referring to, but here
(ZoL 0.7.3) my "man zpool" page shows the following:

       zpool remove pool device ...

           Removes  the  specified  device  from the pool. *This command
currently only supports* removing hot spares, cache, *and log devices*. A
           mirrored log device can be removed by specifying the top-level
mirror for the log. Non-log devices that are part of a mirrored con-
           figuration can be removed using the zpool detach command.
Non-redundant and raidz devices cannot be removed from a pool.



> No mention of "removing" a log file. Why don't you try to detach the log
> device?
>

Because it's not in a mirror, and the same man page above says it's just
for mirrors:

       zpool detach pool device

           Detaches  device  *from  a  mirror*. The operation is refused if
there are no other valid replicas of the data.  If device may be re-
           added to the pool later on then consider the "zpool offline"
command instead.

I just tried the 'detach' anyway and, as expected, it failed complaining
the device is not in a mirror:

zpool status
  pool: pool01
        [...]
        NAME                                               STATE     READ
WRITE CKSUM
        pool01                                             ONLINE
0     0     0
          mirror-0                                         ONLINE
0     0     0
            ata-HGST_REDACTED            ONLINE       0     0     0
            ata-HGST_REDACTED            ONLINE       0     0     0
        logs
          ata-M4-CT256M4SSD3_REDACTED    ONLINE       0     0     0
errors: No known data errors

zpool detach pool01 ata-M4-CT256M4SSD3_REDACTED
cannot detach ata-M4-CT256M4SSD3_REDACTED: only applicable to mirror and
replacing vdevs

If you need any further info, please let me know.

Cheers,
-- 
   Durval.



>
>
> Am 08.12.2017 um 12:45 schrieb Durval Menezes via zfs-discuss:
> > Hello Marco,
> >
> > When (if) you find out, please let me know. AFAIK there's a bug in ZoL
> (and perhaps on FreeBSD ZFS too) that prevents
> > log devices from being removed, so your only solution would be to
> re-create the pool.
> >
> > I have even opened a GitHub ticket for that some time ago, but so far no
> solution has been forthcoming:
> > https://github.com/zfsonlinux/zfs/issues/6677
> >
> > Cheers, and good luck,
> > --
> >    Durval.
> >
> >
> >
> > On Fri, Dec 8, 2017 at 9:28 AM, Marco Glavas via zfs-discuss <
> zfs-discuss at list.zfsonlinux.org
> > <mailto:zfs-discuss at list.zfsonlinux.org>> wrote:
> >
> >     Hi everybody
> >
> >     When I moved my pool from Linux (Ubuntu 16.04) to FreeBSD
> (NAS4Free), I had to leave the log partition behind
> >     (noticed it only after the fact of course).
> >
> >     So the pool was in a degraded state. since NAS4free is a vm, I just
> added a thin provisioned disk and replaced the
> >     faulty one. So far so good.
> >
> >     Only I'd like to give it another, smaller disk to use for logs.
> Therefore I'd like to know if it is at all possible
> >     to remove the log partition from the pool. It is mounted as da1 at
> the moment and I get "pool already exists" error
> >     when trying to remove it.
> >
> >     Anybody have a good idea on how to proceed?
> >
> >     Regards and thank you,
> >
> >     Marco
> >     _______________________________________________
> >     zfs-discuss mailing list
> >     zfs-discuss at list.zfsonlinux.org <mailto:zfs-discuss at list.
> zfsonlinux.org>
> >     http://list.zfsonlinux.org/cgi-bin/mailman/listinfo/zfs-discuss
> >     <http://list.zfsonlinux.org/cgi-bin/mailman/listinfo/zfs-discuss>
> >
> >
> >
> >
> > _______________________________________________
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> > http://list.zfsonlinux.org/cgi-bin/mailman/listinfo/zfs-discuss
> >
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