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Re: Software RAID, a bit OT

To: Ben Gollmer <ben@xxxxxxxxxxxx>
Subject: Re: Software RAID, a bit OT
From: Danny Cox <DCox@xxxxxxxxxxxxxx>
Date: Thu, 18 Jul 2002 07:38:11 -0400
Cc: XFS Mailing List <linux-xfs@xxxxxxxxxxx>
In-reply-to: <B95B1F8C.1E61%ben@jatosoft.com>
References: <B95B1F8C.1E61%ben@jatosoft.com>
Sender: owner-linux-xfs@xxxxxxxxxxx
Ben,

On Wed, 2002-07-17 at 14:20, Ben Gollmer wrote:
> Hope you don't mind me asking this on-list, but I've gotten some very
> helpful storage-related info from here in the past. I'm putting together a
> server for a small group of developers; we have no real budget, so we're
> trying to keep things cheap. Here's our hardware specs so far:
> 
> 2x P3 700 MHz
> 512 MB RAM
> 2 Promise PCI ATA-133 controllers
> 3 Seagate 80 GB HDDs
> 
> This server is going to handle file sharing, e-mail, CVS, and a bug-tracking
> database for us. Our project has some rather large files so we need a good
> amount of storage space. I was planning to software RAID 5 the HDDs together
> for a total of 160 GBs. I have been enjoying XFS on my workstation but I
> know it has had problems with software RAID 5 in the past. Are these
> problems fixed now?

        Since you say you're on a budget, I'd say look for a different
(cheaper) IDE controller.  In the hardware benchmarks (take all
benchmarks with a large grain of salt, of course) I've seen, ATA-133
buys you little at the present time, even IF the drive supports it.  The
drives just aren't that fast yet.

        So, look for another controller, and go for the extra disk.

        The problem with XFS and RAID5 has to do with XFS writing in multiple
block sizes, and how Linux RAID5 implements that.  Steve has been
working on it, and has made it better, but there's still more to do. 
It's better, but by how much, I can't say.

        Given that, pop for the extra disk, and implement a RAID 0+1.  It
should be a bit faster than RAID5, I think.

        The best way is to try it yourself, of course.  Only you know what mix
of software you'll be running.

        As others have noted, the 3ware controllers have been getting lots of
praise on this list.

        Good luck, and let us know what you determine!

-- 
kernel, n.: A part of an operating system that preserves the
medieval traditions of sorcery and black art.

Danny


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