From: antlists <antlists@youngman.org.uk>
To: Aymeric <mulx@aplu.fr>, linux-raid@vger.kernel.org
Subject: Re: mdadm RAID1 with 3 disks active on 2 disks configuration
Date: Sun, 23 Feb 2020 20:40:44 +0000 [thread overview]
Message-ID: <1f5e671c-8d41-695b-2bc4-74df85361e75@youngman.org.uk> (raw)
In-Reply-To: <4cf4cbe7-989e-d7ec-cad9-cfde022bd4bf@aplu.fr>
On 23/02/2020 17:38, Aymeric wrote:
> Hello,
>
> I've a system with a RAID1 using two disks (sda + sdb) + 1 spare (sdc).
>
> For some stupid reason (cable) the spare (sdc) became active and sda was
> out the array.
>
> I then added back sda to the RAID1 but now I've RAID1 with three active
> disks and zero spare.
> I don't understand why the spare device didn't switch back as spare
> after sda have been rebuild.
Because rebuilding sda is a lot of work. The sensible option would have
been to leave sdb and sdc active, and left sda as spare.
> I used the following command to add sda to the RAID1:
> # mdadm /dev/md0 --add /dev/sda3
>
>
> What did I do wrong here? And how to fix it? Do I have to set sdc to
> faulty and add it back?
I'd just leave it as a 3-disk raid. But no, if you do want to set it
back to a 2-disk raid don't do a "faulty and re-add" - that'll just make
re-sync it again. Somehow you've got active devices set to 3, so just
set that back to two. If you look on the wiki it covers the scenario of
converting a three-disk raid to two.
The only thing I will add about a 3-disk raid is that if you want to
change it to anything else, you'll have to revert to 2 first, but do
that when you want to change things, leave it at 3 for the moment.
> Thanks!
Cheers,
Wol
next prev parent reply other threads:[~2020-02-23 20:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-23 17:38 mdadm RAID1 with 3 disks active on 2 disks configuration Aymeric
2020-02-23 20:40 ` antlists [this message]
2020-02-24 9:23 ` Aymeric P.
2020-02-24 9:25 ` Aymeric
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