From: NeilBrown <neilb@suse.de>
To: Michael Busby <michael.a.busby@gmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: Converting from Raid 5 to 6
Date: Tue, 25 Oct 2011 07:14:43 +1100 [thread overview]
Message-ID: <20111025071443.4c497656@notabene.brown> (raw)
In-Reply-To: <CAFsPQ__G3j3CbMDJyYO7BaJrxnPi=MAZFiRfgbruzMhiCVQYag@mail.gmail.com>
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On Mon, 24 Oct 2011 17:03:46 +0100 Michael Busby <michael.a.busby@gmail.com>
wrote:
> should the speed be very slow when doing this progress, its a lot
> slower than a normal grow
Yes.
The array is being reshaped in-place. i.e. data is being read from part of
the array, rearranged, and written back to the same part of the array.
As you can imagine, this is risky - a crash will leave an inconsistent state.
Hence the backup file. Everything in the array is first written to the
backup file, then back to the array. So it is slow.
A "normal" grow is writing to somewhere where there is no valid data, so it
doesn't need the backup.
I do have a plan to make this faster.... but I have lots of plans and little
time.
NeilBrown
>
> reshape = 1.2% (25006080/1953513984) finish=12481.8min speed=2574K/sec
>
> On 24 October 2011 15:11, Mathias Burén <mathias.buren@gmail.com> wrote:
> > On 24 October 2011 14:11, Michael Busby <michael.a.busby@gmail.com> wrote:
> >> At the moment i have a raid5 setup with 5 disks, i am looking to add a
> >> 6th disk and change from raid 5 to raid 6
> >>
> >> having looked at Neil's site i have found the following command, and
> >> just want to double check this is still the recommend way of
> >> converting
> >>
> >> mdadm --grow /dev/md0 --level=6 --raid-disks=6 --backup-file=/home/md.backup
> >>
> >> also would i need to add the extra disk before or after the command?
> >>
> >> cheers
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
> >>
> >
> > Hi,
> >
> > I grew my 6 disk RAID5 to a 7 disk RAID6. First, add the drive. Then
> > partition it as required. Then add the drive to the array (I think
> > it'll become a spare?). Then you can grow it.
> >
> > Make sure you're using the latest mdadm tools available.
> >
> > Regards,
> > Mathias
> >
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
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next prev parent reply other threads:[~2011-10-24 20:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-24 13:11 Converting from Raid 5 to 6 Michael Busby
2011-10-24 14:11 ` Mathias Burén
2011-10-24 16:03 ` Michael Busby
2011-10-24 16:27 ` Mathias Burén
2011-10-24 16:34 ` Michael Busby
2011-10-24 20:14 ` NeilBrown [this message]
2011-10-24 20:19 ` Michael Busby
2011-10-24 20:39 ` NeilBrown
2011-10-24 20:47 ` Michael Busby
2013-11-30 22:13 ` Michael Busby
2013-12-02 5:51 ` NeilBrown
2013-12-02 15:07 ` Michael Busby
2013-12-02 20:38 ` NeilBrown
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