Re: how to configure my new server

I've always had very good performance with Linux's kernel raid, though
I've never compared it to Windows, just to hardware raid cards running in
linux.

I can get aggregate reads of about 48 Megs a second on a pair of 10k 18
gig UW scsi drives in RAID1 config.  I'm not saying there's no room for
improvement, but for what I use it for, it gives very good performance.

Some hardware cards will certainly be faster than the linux kernel
raid software, but it's not a given that any hardware card WILL be faster.
I'm quite certain that you could outrun most older cards using 33 MHz I960
for checksum calculations with a dual 2.4Ghz machine doing software.

The only way to be sure is to test it.

 On Fri, 7 Feb 2003, Peter Darley wrote:

> 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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