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List:       linux-raid
Subject:    Re: RAID 5 faster than RAID 1
From:       "Mike Black" <mblack () csihq ! com>
Date:       2002-03-28 17:07:51
[Download RAW message or body]

Yours sounds close to mine -- I've got 4 x 9 instead of 3x9 with Seagate
ST39140W's synced at 40MB/s on a aic7880: Ultra Wide
Here's my benchmark on a PIII/550:

tiobench.pl
No size specified, using 1024 MB
Size is MB, BlkSz is Bytes, Read, Write, and Seeks are MB/secd . -T

         File   Block  Num  Seq Read    Rand Read   Seq Write  Rand Write
  Dir    Size   Size   Thr Rate (CPU%) Rate (CPU%) Rate (CPU%) Rate (CPU%)
------- ------ ------- --- ----------- ----------- ----------- -----------
   .     1024   4096    1  17.27 13.3% 0.647 1.07% 16.66 33.3% 0.486 0.59%
   .     1024   4096    2  18.38 14.0% 0.797 1.32% 16.32 33.1% 0.494 0.60%
   .     1024   4096    4  18.81 14.2% 0.944 1.53% 16.29 33.0% 0.495 0.60%
   .     1024   4096    8  18.92 14.1% 1.073 1.83% 15.85 33.0% 0.498 0.60%


Individually these drives peg out at 14MB/sec so you do pick up some read
speed with RAID5.

And you won't get 20G from RAID1 -- you'll get 9G (one disk size) with two
mirrors.


________________________________________
Michael D. Black   Principal Engineer
mblack@csihq.com  321-676-2923,x203
http://www.csihq.com  Computer Science Innovations
http://www.csihq.com/~mike  My home page
FAX 321-676-2355
----- Original Message -----
From: "Gernot A. Weber" <gernot@tux-web.de>
To: <linux-raid@vger.kernel.org>
Sent: Thursday, March 28, 2002 11:32 AM
Subject: RAID 5 faster than RAID 1


Hi,

I have a dual PIII-450 with 256MB of RAM here. I would like to build a
RAID 5 array with 3 9,1GB SCSI disks - each on its own channel. Will the
machine be powerfull enough to give a "fast" access to the disks?
Or should I go for a 20GB RAID 1 level?
Will the performance increase with more RAM?
Better use reiserfs or xfs on RAID?

Thanks in advance

   Gernot A. Weber

--
Gernot A. Weber
http://www.tux-web.de

Only wimps use tape backup: _real_ men just upload their important stuff
on ftp, and let the rest of the world mirror it.

                              Linus Torvalds, after a hard drive crash

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