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From: poffen@sj.ate.slb.com (Russ Poffenberger)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: SCSI slowness
Message-ID: <1991Apr3.233137.27935@sj.ate.slb.com>
Date: 3 Apr 91 23:31:37 GMT
References: <1991Apr3.015013.2129@cunixf.cc.columbia.edu>
Reply-To: poffen@SunOS (Russ Poffenberger)
Organization: Schlumberger Technologies, ATE division, San Jose, Ca.
Lines: 35

In article <1991Apr3.015013.2129@cunixf.cc.columbia.edu> liggio@cunixf.cc.columbia.edu (Vincent J. Liggio) writes:
>
>In article <1991Apr02.214925.10627@xstor.com> iverson@xstor.com (Tim Iverson) writes:
>>This is perfectly normal.  The Quantum ProDrive 170S has a maximum sustained
>>transfer rate of about 900KB/s.  The burst rate can be much higher than that,
>>but 900 is the best you'll ever get out of CoreTest.
>>
>>The 170S is actually just your average, every-day, middle of the road,
>>mass-market drive.  If you really want *fast* you should think about
>>Imprimis' Elite (4-5MB/s) or Wren VII or Wren Runner (2-3MB/s).  Of course,
>>*fast* implies *bucks* :-).
>>
>>- Tim Iverson
>>  iverson@xstor.com -/- uunet!xstor!iverson
>
>Interesting, because the drive manual says that the drive can sustain 2.5
>Mb/sec.  And the adapter can do 5 asynchronous, 2.5 mb synchronous (or
>vise-versa).  Doesn't sound like the middle of the road, mass market drive.
>Just a wee bit faster... :-)
>

They are talking more about thoeoritical rates than actual rates. You can get
these high rates if you happen to read from the cache on the drive. However
the maximum rate you can peel off the disk is purely a function of how fast
the bytes fly past the head. This is determined by the rotational rate (usually
3600 RPM for most drives, 5400 coming soon), and the number of sectors per
track. If you read more data than the cache has in it, then the disk rate is
what limits you.

900K/sec sounds reasonable.

Russ Poffenberger               DOMAIN: poffen@sj.ate.slb.com
Schlumberger Technologies       UUCP:   {uunet,decwrl,amdahl}!sjsca4!poffen
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