Path: utzoo!utgpu!water!watmath!clyde!rutgers!cmcl2!nrl-cmf!ames!aurora!labrea!decwrl!sun!pitstop!sundc!seismo!uunet!steinmetz!davidsen
From: davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Help with a Seagate 251 which seems too slow
Message-ID: <9075@steinmetz.steinmetz.UUCP>
Date: 18 Jan 88 19:02:02 GMT
References: <3579@sdcc6.ucsd.EDU>
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Distribution: comp.sys.ibm.pc
Organization: General Electric CRD, Schenectady, NY
Lines: 32

In article <3579@sdcc6.ucsd.EDU> ir1@sdcc6.ucsd.edu.UUCP () writes:

| So, can any one help me out. I would happy if I got the 251 to be as
| fast as the 225, although happier if it were faster. Does anyone
| know the optimal interleave for the 251 with the WD WX1 and an XT.

There is no "best" interleave factor... with a very large interleaf
factor (say 8) everything will run, but slowly. As you decrease the
interleave things will get faster and then slower. The point at which
this occurs depends on your wait states, disk controller, CPU speed,
etc. It *also* depends on the program reading the data. A program which
does read and process will run best with a fairly large interleave (say
4-8), while program loads by DOS (virtually no processing) will run
blindingly fast at interleave 2. What you need to do is repeatedly do a
low level format, high level format, and benchmark until you find out
what works on your system. If you pick 6 for an XT and 4 for an AT you
will be in a reasonable range, since these are the figures used by IBM.

The optimal solution is to use a controller or disk cache program which
does "track buffering." Since this allows the hardware to move the data,
no interleave is needed, and all programs run very fast. We used to do
this on large floppy systems when the PC was still a dream.

The reason Seagate won't tell you what to use is that you have to find
out for yourself, and determine if you want to trade program load for
program run speed, and in which direction. It sounds as if your
interleave is too small, but since you haven't checked it there's no way
to tell.
-- 
	bill davidsen		(wedu@ge-crd.arpa)
  {uunet | philabs | seismo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me