From: Peter Childs <peterachilds@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: setting up raid10 with more than 4 drives
Date: Wed, 30 May 2007 08:29:14 +0100
Message-ID: <a2de01dd0705300029t52ceb76fx25c3ad67db0c43c0@mail.gmail.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0705292227370.6705@asgard.lang.hm>
References: <a97c77030705291918j54b88259ia2f725e8b9e39dd6@mail.gmail.com>
<C2823CFD.31AEB%llonergan@greenplum.com>
<36e682920705292141k9aa038btb543d97cee0fa4a1@mail.gmail.com>
<Pine.LNX.4.64.0705292227370.6705@asgard.lang.hm>
On 30/05/07, david@lang.hm <david@lang.hm> wrote:
>
> On Wed, 30 May 2007, Jonah H. Harris wrote:
>
> > On 5/29/07, Luke Lonergan <llonergan@greenplum.com> wrote:
> >> AFAIK you can't RAID1 more than two drives, so the above doesn't make
> >> sense
> >> to me.
> >
> > Yeah, I've never seen a way to RAID-1 more than 2 drives either. It
> > would have to be his first one:
> >
> > D1 + D2 = MD0 (RAID 1)
> > D3 + D4 = MD1 ...
> > D5 + D6 = MD2 ...
> > MD0 + MD1 + MD2 = MDF (RAID 0)
> >
>
> I don't know what the failure mode ends up being, but on linux I had no
> problems creating what appears to be a massively redundant (but small)
> array
>
> md0 : active raid1 sdo1[10](S) sdn1[8] sdm1[7] sdl1[6] sdk1[5] sdj1[4]
> sdi1[3] sdh1[2] sdg1[9] sdf1[1] sde1[11](S) sdd1[0]
> 896 blocks [10/10] [UUUUUUUUUU]
>
> David Lang
>
>
Good point, also if you had Raid 1 with 3 drives with some bit errors at
least you can take a vote on whats right. Where as if you only have 2 and
they disagree how do you know which is right other than pick one and hope...
But whatever it will be slower to keep in sync on a heavy write system.
Peter.
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To: pgsql-performance@postgresql.org
Cc: peterachilds@gmail.com
Subject: Re: setting up raid10 with more than 4 drives
In-Reply-To: <a2de01dd0705300029t52ceb76fx25c3ad67db0c43c0@mail.gmail.com>
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