Re: how to configure my new server

Folks,
    I'm going to be setting up a Linux software RAID this weekend, and in my
research I cam across the following document:
http://www.hpl.hp.com/techreports/2002/HPL-2002-352.html
    It says that Linux software RAID is slower than XP Software RAID on the
same hardware.  If this is the case, wouldn't it follow that hardware RAID
has a really good chance of beating Linux software RAID?  Or does the
problem that affects the software raid affect all Linux disk IO?  I'm not
really knowledgeable enough to tell.
Thanks,
Peter Darley

-----Original Message-----
From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-owner@postgresql.org]On Behalf Of
scott.marlowe
Sent: Friday, February 07, 2003 8:13 AM
To: Andreas Pflug
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] how to configure my new server


On Fri, 7 Feb 2003, Andreas Pflug wrote:

> Actually, I don't trust software RAID. If I'm talking about RAID, I
> mean mature RAID solutions, using SCSI or similar professional
> equipment.

Funny you should mention that.  A buddy running a "professional" level
card had it mark two out of three drives in a RAID 5 bad and wouldn't let
him reinsert the drives no matter what.  Had to revert to backups.

I'll take Linux's built in kernel raid any day over most pro cards.  I've
been using it in production for about 3 years and it is very mature and
stable, and lets you do what you want to do (which can be good if your
smart, but very bad if you do something dumb... :-)

I've had good and bad experiences with pro grade RAID boxes and
controllers, but I've honestly had nothing but good from linux's kernel
level raid.  Some early 2.0 stuff had some squirreliness that meant I had
to actually reboot for some changes to take affect.  Since the 2.2 kernel
came out the md driver has been rock solid.  I've not played with the
volume manager yet, but I hear equally nice things about it.

Keep in mind that a "hardware raid card" is nothing more than software
raid burnt into ROM and stuffed on a dedicated card, there's no magic
pixie dust that decrees doing such makes it a better or more reliable
solution.


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