Re: how to configure my new server - Mailing list pgsql-performance

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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