Re: FreeBSD 5.3b7and poor ata performance

From: Julian Elischer <julian_at_elischer.org>
Date: Tue, 19 Oct 2004 14:12:58 -0700
Mike Jakubik wrote:

>Julian Elischer said:
>  
>
>>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.
>>>
>>>      
>>>
>>I BELIEVE (without empirical proof) that the new scheme of running IO
>>through the geom threads
>>requires a higher degree of smartness from the scheduler than before,
>>where IO was done either by interrupt
>>or by the calling (already running) thread.
>>
>>Make sure you have preemption enabled, and make sure that HTT is turned
>>off. (HTT is a DOG that slows down
>>almost everything except processes that have a lot of FP work).
>>    
>>
>
>I do not use GEOM, all GEOM related stuff is is disabled from the kernel.
>HTT is disabled in the bios already. Im using SCHED_4BSD, no prememtion
>however. I will update this box to a more recent releng_5 soon, and try
>again. Still, this seems pretty bad for server class hardware.
>

How do you disable GEOM? I believe it is no longer optional. Everythi g 
runs through geom. you may however
be not installing some modules..



>
>  
>
Received on Tue Oct 19 2004 - 19:12:58 UTC

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