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Re: Everyone's favorite offtopic topic

To: linux-xfs@xxxxxxxxxxx
Subject: Re: Everyone's favorite offtopic topic
From: Robin Humble <rjh@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Sun, 29 Jul 2001 21:47:20 +1000 (EST)
In-reply-to: <4.3.2.7.2.20010729113909.03a12bc8@pop.xs4all.nl> from "Seth Mos" at Jul 29, 2001 12:23:36 PM
Sender: owner-linux-xfs@xxxxxxxxxxx
Seth Mos writes:
>There recently was a message about building a $5000 dollar IDE raid on
>slashdot IIRC.
>Don't know the URL anymore.

  http://staff.sdsc.edu/its/terafile/

>Basic configuration was purchasing a large case which can house 16 disks
>Purchase 16 100GB Maxtor IDE disks (the 540DX uses less power)
>Purchase 2 3ware Escalade 6800 controllers
>A PC for booting the machine.

I was disapointed by this article. It was way more than $5k (probably
that was Slashdot's mistake) which is to be expected for 16 disks
I guess, however their performance barchart (which looks impressive)
bears little relation to the numbers in their spreadsheet. 
In particular their RAID5 write numbers are kinda low at ~18MB/s.
The newer 7000 series 3ware cards might be better???

Anyway - our latest datapoint:
Initial setup tests of our XFS RAID box with a lowly pentium 450, eight
75G 7200rpm IBM drives, and two Promise Ultra100 Tx2 controller cards,
cvs xfs kernel, seem to indicate that we can get around 40MB/s RAID5
writes. Alternatively we can double their 50-60MB/s RAID0 reads to around
110MB/s(!). We were pretty happy to see those numbers :)
We're still setting up the machine (these are from late last night so
should maybe be taken with a grain of salt) and are moving to faster
memory and cpu soon, so hope to see them improve.  Also one of our
disks is misbehaving and probably is dragging the numbers down. I
should try bonnie++ with 4x memory size and not just the default 2x
also - that may lower our numbers a bit and remove more caching effects.
We haven't played with chunk sizes, mkfs options, mount options, or
external logs yet.

I also tried the SDSC folks 'fastest' 2xRAID5 + RAID0 configuration,
but it was no quicker than just a RAID5 over all 8 disks. I guess
they're seeing some artifacts from their 3ware cards/drivers.

XFS seemed slightly slower (5%?) than ext2 for the tests we've run so
far. We're running some NFS tests over 100Mbit now. Gigabit will follow
once we have another cat5 gigabit card somewhere to write from! :)

cheers,
robin


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