Re: FreeBSD 5.3b7and poor ata performance

From: Mike Jakubik <mikej_at_rogers.com>
Date: Tue, 19 Oct 2004 16:18:12 -0400 (EDT)
Xin LI said:

> 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 :-(

Hrm, i tried your block size, and the performance is even worse:

# dd if=/dev/da0 of=/dev/null bs=131072 count=2000
2000+0 records in
2000+0 records out
262144000 bytes transferred in 8.688651 secs (30170852 bytes/sec)
Received on Tue Oct 19 2004 - 18:18:19 UTC

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