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From: johnhlee@CS.Cornell.EDU (John H. Lee)
Subject: Re: A3000 hard drive capacity
Message-ID: <1991May29.013321.18565@cs.cornell.edu>
Sender: news@cs.cornell.edu (USENET news user)
Nntp-Posting-Host: fulla.cs.cornell.edu
Reply-To: johnhlee@cs.cornell.edu (John H. Lee)
Organization: Cornell Univ. CS Dept, Ithaca NY 14853
References: <1991May20.102326.27503@NCoast.ORG> <192e8a94.ARN00a5@core.north.de> <42674@cup.portal.com>
Date: Wed, 29 May 1991 01:33:21 GMT
Lines: 33

In article <42674@cup.portal.com> FelineGrace@cup.portal.com (Dana B Bourgeois) writes:
[...]
>I've got another question (to keep you gurus on your toes :->).  SCSI
>has a block address limit of about 1.2 Gig for 512 Byte blocks.  If I
>buy a 2.0 Gig drive and partition the drive into at least two logical
>drives, do I avoid this problem?  This is a serious question.  I ordered
>a SPARC 2 with a pair of 2.0 Gig drives for work and I'm not sure what
>will happen when we format them.  So enlighten me O gurus.

The problem is that some disk drivers use the non-extended SCSI commands
for block address over 1.2Gb (21 bits address for a 512 byte block) and
inadvertantly "wrap-around" and access the lower blocks.  This is not
an inherit bug in the SCSI drives or protocol, but a bug in the disk
drivers.  (NOTE:  "extended" SCSI commands do not mean "non-standard",
just that they have more bits for block addresses and other things.)

The drive does nothing with regard to partitioning; only the system
software cares about this.  Partitioning the drive will ensure you don't
access blocks over 1.2Gb, but the faulty drivers still can't access
partitions containing blocks at locations over 1.2Gb.  In other words,
you can still only use 1.2Gb of the 2.0Gb drive.

You should ask your disk-driver software vendor.  As far as I know, this
problem cropped up on DEC VMS and Ultrix disk-drivers, and should be fixed
by now.  I don't know if SPARCstation SunOS disk-drivers have the same
problem.  I believe that the AmigaDOS 2.0 scsi.device also had this problem
but that it is now also fixed.  Fujitsu was recommending you treat 2.0Gb
drives as 1.2Gb drives until you receive corrected drivers.

-------------------------------------------------------------------------------
The DiskDoctor threatens the crew!  Next time on AmigaDos: The Next Generation.
	John Lee		Internet: johnhlee@cs.cornell.edu
The above opinions are those of the user, and not of this machine.