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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!ames!ncar!gatech!rayssd!galaxia!dave
From: dave@galaxia.Newport.RI.US (David H. Brierley)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: Step rate change (WD2010) Some Benchmarks ... (was Re: WD2010 / No ECC)
Keywords: iv, VHB, WD2010, WD1010, disk controller, step rate, faster?
Message-ID: <832@galaxia.Newport.RI.US>
Date: 24 Aug 89 02:17:26 GMT
References: <1624@mtunb.ATT.COM> <1182@mitisft.Convergent.COM> <947@icus.islp.ny.us>
Reply-To: dave@galaxia.Newport.RI.US (David H. Brierley)
Organization: Dave's Very Own Personal System
Lines: 33

In article <947@icus.islp.ny.us> lenny@icus.islp.ny.us (Lenny Tropiano) writes:
>In article <1182@mitisft.Convergent.COM> dold@mitisft.Convergent.COM 
>(Clarence Dold) writes:
>...
>|>Try setting the Step Rate in an iv.desc file to 14 instead of 0, 
>|>then iv -u the disk.  No loss of data, just a 20% increase in seek 

>Ok, call me brave, but I had to try it...  It sorta was a test for my WD2010

># /bin/time /bin/dd if=/dev/rfp002 of=/dev/null bs=100k

>Nada .. Oh well, for this long winded explanation, essentially you
>can't improve the seek performance by 20% ...

But you didn't test seek performance, you tested straight sequential access
to the raw disk.  If you want to test seek performance you have to get the
heads to go back and forth and all around.  To really test seek performance
you would need a special program that did random seeks on the disk, but a
quick approximation might be achieved with:
	"find / -print | cpio -oB >/dev/null"
This will at least cause the heads to jump around a little more than the "dd"
would.

If this trick really can improve seek performance it would be a great boon
to people with limited amounts of memory (i.e. <= 1 meg) because most of the
performance degradation on the machine is caused by frequent accesses to the
swap area.  An access to the swap area requires a seek back to the beginning
of the disk, an i/o, and then another seek back to wherever you had the heads
positioned previously.
-- 
David H. Brierley
Home: dave@galaxia.Newport.RI.US   {rayssd,xanth,lazlo,mirror,att}!galaxia!dave
Work: dhb@rayssd.ray.com           {sun,uunet,gatech,necntc,ukma}!rayssd!dhb