High CPU = Poor disk I/O on Svr2003?

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Date:         Wed, 6 Oct 2004 12:05:51 -0400
To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM

 
Russ,

I know this isn't a very "technical" posting, but wondering if you can
pass it along because it's somewhat disturbing and confusing.

On Windows Server 2003:

Given a process running at low priority consuming 100% processor time,
any normal (or higher) priority process will have very slow disk access.

The process in question is SETI running priority level 4. While this
low priority process is running, any disk I/O is less than half its
normal speed, sometimes disk I/O drops as much as 80%.

This occurs on Windows Server 2003 but not on anything previous. We
have tested on multiple Svr 2003 machines with different disk
configurations (IDE and SCSI, Hardware RAID and stand alone disks) and
have the same results on each. Performance settings on all machines
were set to adjust Processor Scheduling and Memory usage for "Programs"
though changing this setting didn't have any affect. Windows XP, 2000
and NT do not exhibit this behavior.

Can anyone else verify this? Shouldn't the scheduler be releasing CPU
time for the low priority apps to disk I/O processes that need the
time? What is wrong with Server 2003?

Thanks.

Joe Pochedley

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