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From: iglesias@draco.acs.uci.edu (Mike Iglesias)
Newsgroups: comp.unix.ultrix,comp.periphs.scsi
Subject: Re: ANy joy with 3rd party SCSI disks on DS3100?
Message-ID: <270379F7.4803@orion.oac.uci.edu>
Date: 28 Sep 90 16:27:35 GMT
References: <1990Sep25.083654.9716@brolga.cc.uq.oz.au> <MNWQ8D2@dri.com> <9750@ccncsu.ColoState.EDU>
Reply-To: Mike Iglesias <iglesias@draco.acs.uci.edu>
Organization: University of California, Irvine
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In article <9750@ccncsu.ColoState.EDU> rsk@oldfield.tmc.edu (Rich Kulawiec) writes:
>I've got four DS3100's connected to CDC Wren V's; in fact one of them
>has four of these drives plus an exabyte.  Works like a champ.
>
>I'm running them without the cache-readahead bit turned on, by the
>way; my understanding is that the two ways to turn on that bit
>were (1) hook up the drive to a Sun-4 and use its disk formatter
>to enable the bit or (2) hook up the drive to a NeXT and use the
>program posted by Paul O'Neill some time ago.  Well, I haven't got
>either machine, so my drives are still running without that bit set.

Under Ultrix 4.0, I've used /etc/rzdisk to change the "readahead cache
disable" (RCD) bit on Maxtor drives.  You want the bit to be 0 to
enable the readahead cache.  I used the following command:

  # /etc/rzdisk -c ask /dev/rrzxc

where the 'x' in /dev/rrzxc is the drive number you want to tweak.

I just check one of our 5000s with a CDC drive on it, and it appears that
this bit is not in the same place as it is on the Maxtor drives (page 8
of the drive parameters), so I guess you're out of luck using rzdisk
on CDC drives.


Mike Iglesias
University of California, Irvine
Internet:    iglesias@draco.acs.uci.edu
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