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Date:      Wed, 18 Sep 2002 21:32:08 -0700
From:      Lars Eggert <larse@ISI.EDU>
To:        Steve Fettig <lists@stevenfettig.com>
Cc:        David Burns <david.burns@dugeem.net>, net@freebsd.org
Subject:   Re: Network Transfer Speed Issues - Tweaks/Advice?
Message-ID:  <3D895348.3000706@isi.edu>
References:  <F6AF9956-CB84-11D6-BDD9-00039384AB84@stevenfettig.com>
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[-- Attachment #1 --]
Steve,

your setup is way to complex. As David suggested, first try to establish 
whether the network connection between the two machines is the problem 
or not. Forget about NFS for now, just benchmark TCP and UDP (which do 
you NFS mount over, by the way?) If network performance is erratic, 
isolate the setup from cross traffic, and swap out NICs, hubs and or 
switches.

Only after you've ruled out the network would I start worrying about 
disks, controllers and NFS settings.

The idea here is to change ONE parameter in the setup at a time, and 
rerun your benchmark of choice.

Steve Fettig wrote:
> I really appreciate everyone who offered up a few ideas and answers.  
> One of the first things I finally figured out was that the adapter was 
> failing... hmmm doesn't make sense - it didn't fail completely, but I 
> swapped it out with a different adapter (same thing 2940UW) and the 
> performance change was quite remarkable.  That still didn't solve the 
> huge discrepancy in speed difference between my other SCSI (internal) 
> drives and the ones I am working with, however.  My next test will be to 
> build a system from the ground up w/ a 500 MHz processor and a 133 MHz 
> FSB.  I am also wondering if I really missed the boat on the drives, 
> too.  They are "older" 5400 RPM SCSI drives (HUGE drives physically) but 
> I don't see how they would be any slower than an IDE 5400 RPM drive - 
> which they are and quite a bit so.
> As for all of the other stuff, the CPU load is usually at a steady 15% 
> (nfsd).  Since that is the only service running (besides the required 
> daemons on a somewhat vanilla system) and the only load that the 
> "server" is under, I don't think that is an issue.  I am going to test 
> system performance with the suggested programs (that was another thing I 
> was looking for in the answer, although I guess I didn't say it...) and 
> see what happens.  I am starting to think that this is a combination of 
> controller and system not having the performance I was expecting.  
> Everything on the net end seems to be functioning without problem - no 
> lost packets, broken communication, etc.
> 
> Well, the testing goes on.  Please continue to comment if you have any 
> ideas (especially with regards to kernel tweaks, etc).
> 
> Thanks,
> Steve
> 
> On Tuesday, September 17, 2002, at 07:55 , David Burns wrote:
> 
>> Steve Fettig wrote:
>>
>>> I recently set up an NFS server to run daily backups on.  The server 
>>> was built using an old P150 w/ 90 MB of ram and a 6GB hard drive.  
>>> (All servers in this experiment are set up using FBSD 4.6.2 and the 
>>> client is a Mac PowerBook G4 running Mac OS X.)  Attached to it is an 
>>> external SCSI hard drive enclosure with 4 47GB SCSI drives running 
>>> off an AHA-2490UW SCSI adapter.  I am getting really odd performance 
>>> when doing an NFS transfer (I also get odd performance out of scp) 
>>> from the machine I am trying to back up.  I will get a burst of 
>>> 20Mbps for about 30 seconds, then it will ramp down to 1 Mbps for 
>>> about 2 minutes, ramp backup to 20 Mbps, then back down to 1 Mbps and 
>>> so on.
>>
>> You need to break the problem down ... Is the system CPU and/or IO 
>> bound during the backup? Also try some quick benchmarks to verify 
>> basic system performance levels: Network IO - use ttcp (or netperf 
>> etc), and Disk IO - use bonnie (or similar).
>>
>> NB Of course you can't simply take such benchmarks results and put 
>> them together - but you will gain a better understanding of where the 
>> potential slowdowns may be.
>>
>> Lastly, performance issues on older Pentiums can also result from poor 
>> memory bandwidth and/or PCI chipset problems. I recently replaced a 
>> P120 with a Celeron 333 - the performance improvement was surprising.
>>
>> Regards,
>> David
>>
> 
> 
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> with "unsubscribe freebsd-net" in the body of the message


-- 
Lars Eggert <larse@isi.edu>           USC Information Sciences Institute

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