From: Neil Brown <neilb@cse.unsw.edu.au>
To: David Anderson <david.anderson@calixo.net>
Cc: linux-raid@vger.kernel.org
Subject: Re: Software RAID within RAID
Date: Fri, 25 Jul 2003 12:15:50 +1000 [thread overview]
Message-ID: <16160.37590.474862.361114@gargle.gargle.HOWL> (raw)
In-Reply-To: message from David Anderson on Friday July 25
On Friday July 25, david.anderson@calixo.net wrote:
> Hi all,
>
> First of all I would like to thank the developers of the linux software
> RAID system for their excellent work which has saved my data on several
> occasions.
>
> Recently I lost one of the disks on my software RAID5 (3x2Gb SCSI on a
> 2.4.21 Debian Woody). Seeking replacements, I came across two 4Gb SCSI
> drives. After inserting one of them as a temporary replacement for the
> dead 2Gb, I am now looking into ways of better integrating these two new
> disks into my existing setup.
>
> The most best solution I came up with was to extend the array's overall
> capacity from 4 to 8Gb. To do this I would first combine the two
> remaining 2Gb disks into a RAID0 array, and then combine that array and
> the two 4Gb disks into a RAID5 array. To clarify this, here is a diagram
> of this solution: http://polaris-outpost.net/vrac/Solution.png .
>
> However, there are a few things I would like to know before I make an
> attempt at this setup. First of all, would the software-raid driver
> handle disk failures properly even with the RAID within RAID? I do not
> see why not, but I'd rather be sure before I jump...
Yes. This definately works.
Though it wouldn't hurt for you to simulate a failure just to convince yourself.
> The other question I have is about performances. Would the RAID0 array
> significantly impact on the overall I/O perfomances of the RAID5 array?
> If anyone has already had the opportunity of comparing performances on a
> regular RAID5 and a RAID5 containing a RAID0, I would be interested in
> the results. I will of course conduct my own tests once this setup is in
> place.
I haven't tested it myself (though I have a setup rather like this
running at the moment: used to 36Gig drives while waiting for a
failed 72Gig drive to be replaced).
NeilBrown
>
> Thanks in advance for your help
> David Anderson
> -
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prev parent reply other threads:[~2003-07-25 2:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-25 1:48 Software RAID within RAID David Anderson
2003-07-25 2:15 ` Neil Brown [this message]
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