[zfs-discuss] Removing log device from existing pool

Durval Menezes durval.menezes at gmail.com
Fri Dec 8 07:32:02 EST 2017


Hi Uwe,

On Fri, Dec 8, 2017 at 10:16 AM, Uwe Sauter via zfs-discuss <
zfs-discuss at list.zfsonlinux.org> wrote:

>
> @Durval
> I'm running ZFS on Gentoo, from Git HEAD from a few days ago (just for
> version info).
>
> The quotation is from the zpool man page's "Intent log" section, not from
> one of the zpool subcommands.
>

Thanks for the clarification. I just checked the "Intent Log"section on my
"man zpool" and it shows exactly the same thing you quoted.

Therefore, I think we have an internal inconsistency in the docs, as the
two sections on the same manpage (ie, "zpool remove" and "Intent log"
sections are in disagreement).

I think this is a (documentation) bug. Can you file it, or should I?



> But yes, you are right, "attach" and "detach" only apply to mirror
> sub-devices. Apologies…
>

No problem, and in case of need, I stand ready to help debug this.


> @Marco
> It would be beneficial if you could provide some kind of log so others can
> retrace exactly what you tried to do…
>

Marco, perhaps you should consider contacting the FreeBSD/FreeNAS folks
directly. I have had need to talk with them in the past (I also sysadmin a
few FreeNAS/FreeBSD boxes) and got excellent support on the #freenas and
#freebsd channels on irc://freenode.net

Cheers,
-- 
   Durval.




>
>
>
> Am 08.12.2017 um 13:03 schrieb Durval Menezes:
> > Hello Uwe,
> >
> > On Fri, Dec 8, 2017 at 9:48 AM, Uwe Sauter via zfs-discuss <
> zfs-discuss at list.zfsonlinux.org
> > <mailto: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 <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>
> >     > <mailto: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
> >     >     _______________________________________________
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> discuss
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> >     >
> >     >
> >     >
> >     >
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