[Beowulf] Re: SATA or SCSI drives - Multiple Read/write speeds.

Robin Laing Robin.Laing at drdc-rddc.gc.ca
Wed Dec 10 11:32:56 EST 2003


Robert G. Brown wrote:
> On Tue, 9 Dec 2003, Robin Laing wrote:
> 
> 
>>I agree but I am not looking at swap thrashing in the sense of many 
>>small files.  I am looking at 1 or 2 large files that are bigger than 
>>memeory while working.  I know on my present workstation I will work 
>>with a file that is 2X the memory and I find that the machine stutters 
>>(locks for a few seconds) every time there is any disk ascess.  I 
>>would like to add more ram but that is impossible as there are only 
>>two slots and they are full.  Management won't provide the funds.
> 
> 
> I have to ask.  Is it a P4?  Strictly empirically I have experienced
> similar things even without filling memory.  I actually moved my
> fileserver off onto a Celeron (which it has run flawlessly) because it
> was so visible, so annoying.

Dell P4 with 512M ram.  IDE drive.

> 
> I have no idea why a P4 would behave that way, but to my direct
> experience at least some P4-based servers can be really BAD on file
> latency for reasons that have nothing to do with the disk hardware or
> kernel per se.  Maybe some sort of chipset problem, maybe related to the
> particular onboard IDE/ATA controllers -- I never bothered to try to
> debug it other than to move the server onto something else where it
> worked.  AMD or Celeron or PIII are all just fine.
Even more reason for me to stick with AMD's.
> 
> If you're stuck on the hardware side with no money to get better
> hardware, well, you're stuck.  My P4 system had plenty of memory and a
> 1.8 MHz clock and still was a pig compared to a 400 MHz Celery serving
> the SAME DISK physically moved from one to the other.
> 
>    rgb
> 

I find that my P90 at home with UWSCSI is faster most of the time than 
my computer at work.

This thread has sure opened up some debate.  I didn't think it would 
raise the number of issues it has.

-- 
Robin Laing

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