[Novalug] swap / raid

[Roger W. Broseus]

I was curious so googled (sp?)  "swap raid linux" --


    2.3 Swapping on RAID

There's no reason to use RAID for swap performance reasons. The kernel 
itself can stripe swapping on several devices, if you just give them the 
same priority in the |/etc/fstab| file.

A nice |/etc/fstab| looks like:

/dev/sda2       swap           swap    defaults,pri=1   0 0
/dev/sdb2       swap           swap    defaults,pri=1   0 0
/dev/sdc2       swap           swap    defaults,pri=1   0 0
/dev/sdd2       swap           swap    defaults,pri=1   0 0
/dev/sde2       swap           swap    defaults,pri=1   0 0
/dev/sdf2       swap           swap    defaults,pri=1   0 0
/dev/sdg2       swap           swap    defaults,pri=1   0 0

This setup lets the machine swap in parallel on seven SCSI devices. No 
need for RAID, since this has been a kernel feature for a long time.

Another reason to use RAID for swap is high availability. If you set up 
a system to boot on eg. a RAID-1 device, the system should be able to 
survive a disk crash. But if the system has been swapping on the now 
faulty device, you will for sure be going down. Swapping on a RAID-1 
device would solve this problem.

http://www.linux.com/base/ldp/howto/Software-RAID-HOWTO-2.html

See also:


      RAID-1, Part 2


        August 14th, 2002 by Joe Edwards, Malmin
        <http://www.linuxjournal.com/user/1001244> and Ron Shaker
        <http://www.linuxjournal.com/user/1001245> in

            * SysAdmin <http://www.linuxjournal.com/taxonomy/term/21>

How to make a RAID-1 swap device and how to boot from a RAID-1 device, 
using RAID-1 to facilitate disk backups.
http://www.linuxjournal.com/article/5898

BUT, don't send me no questions: I know less than what I don't know.

--
    Roger W. Broseus - Linux User
    Email: RogerB at bronord.com
    Web Site: www.bronord.com



novalug-request at calypso.tux.org wrote:

Message: 2
Date: Wed, 18 Mar 2009 18:26:55 -0700 (PDT)
From: Brandon Saxe <brandon20va at yahoo.com>
Subject: [Novalug] Any ideas on this weird issue?
To: novalug mailing list <novalug at calypso.tux.org>
Message-ID: <100561.59768.qm at web50811.mail.re2.yahoo.com>
Content-Type: text/plain; charset=us-ascii


I am running Ubuntu 8.04 LTS on my desktop. I am using software RAID1. Every so often X would lock up or crash and reboot. This would happen every 2-3 days. Recently, I added a different disk and moved my swap space there. Ever since the move, X has not crashed once. It's probably been two weeks now and the crash has not occurred. What's interesting is that swap is hardly ever used. I have 3gig RAM. The old swapfile was on the RAID1.

Does anybody have any thoughts as to why moving my swap off of the RAID1 *seems* to have made my system more stable? This is the only thing I can think of that has changed.

Seems weird to me, but with computers I know that just about anything is possible and probably can be explained somehow.

--Brandon

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