Re: FreeBSD 5.3b7and poor ata performance

From: Mike Jakubik <mikej_at_rogers.com>
Date: Tue, 19 Oct 2004 23:45:18 -0400 (EDT)
Scott Long said:
> Xin LI wrote:
>> Hi, Mike
>>
>> On Tue, Oct 19, 2004 at 04:18:12PM -0400, Mike Jakubik wrote:
>>
>>>Xin LI said:
>>>
>>>
>>>>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)
>>
>>
>> You may want to try other block sizes, like 65536, 262144, 524288,
>> 1048576
>> or so.  The peak performance block size depends heavily on hardware...
>>
>> Cheers,
>
> This won't really matter.  physio will chop the blocks up into 128k
> segments, and GEOM will cut them again into 64k segments.  Other than
> a minor amount of coelscing in these stages, it won't make a difference.

Considering phk's comments, i still find it odd that a scsi based (brand
new seagate cheetahs) raid 10 array would perform so poorly in transfer
rates compared to a single ata drive. I ran diskinfo -t on the array, and
it just confirmed that the transfer rates are lacking, the seek rate is
however 3x as fast as the ata drives.
Received on Wed Oct 20 2004 - 01:45:26 UTC

This archive was generated by hypermail 2.4.0 : Wed May 19 2021 - 11:38:18 UTC