Re: FreeBSD 5.3b7and poor ata performance

From: Xin LI <delphij_at_frontfree.net>
Date: Wed, 20 Oct 2004 04:09:08 +0800
Hi, Mike,

On Tue, Oct 19, 2004 at 02:46:32PM -0400, Mike Jakubik wrote:
> Out of curiosity, i ran this on one of our production servers, which runs
> on a dual Xeon MB, with SCSI raid-10 setup, and to my surprise here are
> the results:
> 
> CPU: Intel(R) Xeon(TM) CPU 2.80GHz (2799.22-MHz 686-class CPU)
> real memory  = 2146959360 (2047 MB)
> avail memory = 2099650560 (2002 MB)
> FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
> 
> da0 at asr0 bus 0 target 0 lun 0
> da0: <ADAPTEC RAID-10 3B0A> Fixed Direct Access SCSI-2 device
> 
> FreeBSD 5.3-BETA4 #0: Sun Sep 12 13:09:43 EDT 2004
> 
> (Custom kernel, no debugging)
> 
> # dd if=/dev/da0 of=/dev/null bs=1m count=200
> 200+0 records in
> 200+0 records out
> 209715200 bytes transferred in 6.225309 secs (33687517 bytes/sec)
> 
> Why is a SCSI raid-10 system slower than a plain IDE disk? Something is
> wrong here.

Unfortunatelly I can reproduce similiar problem when using Ultra320 under
mpt(4) and a version of Adaptec's SCSI card (maybe aic, or something else,
which I have to go to my office to find out).  Additionally the problem is
not FreeBSD specific, with a Linux installation, it shows poor performance
too.  (No RAID configuration, though).

I found that block size does influence performance greatly.  With a block
size of 131072 I got peak read performance at about 70MB/s, but that's all.
I did not have the necessary knowledge at the time I have did the test last
month, so I got only the result and thought that I have made something
wrong and hoped someone to correct me with no luck :-(

Cheers,
-- 
Xin LI <delphij frontfree net>	http://www.delphij.net/
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Received on Tue Oct 19 2004 - 18:09:32 UTC

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