[NTLUG:Discuss] Disk performance.

[Greg Hewett]

you can test you read timings with the command:
  hdparm -t <device> 

For Example: hdparm -t /dev/hda

There are many areas that affect the I/O of you drives.  Your pci bus is
shared, so if you are sharing the bus with other I/O intensive devices, then
there will be problems.

I think that you need to go to SCSI.  SCSI is said to be able to push 60-70
Mbytes/second.  I do not think you can get close to that with the type of
reads that you are doing and with one spindle.  A raid array would really help
you get the most performance out of your SCSI bus because your data would be
on several spindles.

Where to go from here?  When suggesting a solution I have a co-worker that
says pick 2... Good, Fast, or Cheap.  This all depends on the importance of
the data.

  Raid Array - not cheap
  Single SCSI disk - not good
  Software Raid - not fast.

greg

On Wed, Dec 13, 2000 at 03:30:30PM -0600, Steve Baker wrote:
> 
> Does anybody here have much experience of measuring disk drive throughput
> rates?   It's an area of PC computing that I know very little about.
> 
> I have an application that needs to load large (multi-megabyte) files very
> quickly from disk for long, sustained periods.  The nature of what I'm doing
> means that caching data in RAM won't help because I don't read the same
> file twice (well, not until we've loaded many, many Gigabytes of other stuff
> along the way).
> 
> On my PC here at home (which has a 450MHz CPU and a vanilla low-end 20Gb
> IDE drive) I'm managing to load about 5Mbytes/sec. (These files are 'PNG'
> images - and they have to be uncompressed on-the-fly).
> 
> My question is - if I go out and pick a good disk drive - or several
> drives - SCSI or IDE or whatever else works - or perhaps a RAID array
> or something - slap in a 1GHz CPU on a good motherboard...what kind of
> speedup would you expect I would get?
> 
> I'm hoping to get at least 20Mbytes/sec - more would be good.
> 
> -- 
> Steve Baker   HomeEmail: <sjbaker1 at airmail.net>
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                     Greg Hewett <ghewett at d-techcorp.com>   
                   PHONE:  972.588.3565  FAX:  972.588.3551
                              www.D-TechCorp.com
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