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Date:      Fri, 26 Feb 1999 08:09:49 -0500
From:      Daniel Veillard <Daniel.Veillard@w3.org>
To:        Doug Ledford <dledford@redhat.com>
Cc:        "Robert G. Brown" <rgb@phy.duke.edu>, Maxwell Spangler <maxwell@clark.net>, AIC7xxx@FreeBSD.ORG
Subject:   Re: Adaptec 7890 and RAID portIII RAID controller Linux Support
Message-ID:  <19990226080949.F29876@w3.org>
In-Reply-To: <36D5B02F.B9E0605C@redhat.com>; from Doug Ledford on Thu, Feb 25, 1999 at 03:18:55PM -0500
References:  <Pine.LNX.3.96.990225124113.3721A-100000@ganesh.phy.duke.edu> <36D5B02F.B9E0605C@redhat.com>

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> That's possible, but what I've found to be a good method is to do something
> like this:
> 
> /dev/sda1: 200MB
> /dev/sda2: Rest of disk
> 
> Then I copy that exact same paritioning to all the rest of the disks.  When I
> actually lay it out, /dev/sda1 becomes the self sustaining /boot partition and
> /dev/sdb1, /dev/sdc1, /dev/sdd1, etc all become identical swap partitions that
> are all set up with exactly the same priority level in the fstab.  This way,
> all the swap partitions end up being their own psuedo raid stripe, but they
> bypass the VFS code and go directly into the block driver.  They are also

  I have a problem with that: We are running here RAID 5 systems,
the goal is to aproach 100% uptime as much as possible, hence RAID is
used as a way to resist disk failures. If you stripes your swap space
among those drives bypassing the redundancy layer from the RAID, you
loose the ability to resist disk failures. Especially with identical
priorities, if you're using the swap even only a bit, taht mean that 
some dirty data owned by a running process will be on the failed drive
and basically you will have to reboot to regain a functionning system.
  From a performance point of view, it looks silly to have swap running
on top of RAID 5 (or even RAID 3) but this ensure that your system will
stay up if one of the RAID'ed drives goes down.

  my 2cents,

Daniel

-- 
	    [Yes, I have moved back to France !]
Daniel.Veillard@w3.org | W3C, INRIA Rhone-Alpes  | Today's Bookmarks :
Tel : +33 476 615 257  | 655, avenue de l'Europe | Linux, WWW, rpmfind,
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http://www.w3.org/People/W3Cpeople.html#Veillard | badminton, and Kaffe.


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