Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!coherent!dplatt
From: dplatt@coherent.com (Dave Platt)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Apple HD SC Setup partitionning
Summary: There _is_ a reason!
Message-ID: <24232@coherent.com>
Date: 28 Apr 89 06:08:27 GMT
References: <892@cnetlu.UUCP> <12994@pasteur.Berkeley.EDU>
Reply-To: dplatt@coherent.com (Dave Platt)
Organization: Coherent Thought Inc., Palo Alto CA
Lines: 58

In article <12994@pasteur.Berkeley.EDU> dean@venus.Berkeley.EDU writes:
> In article <892@cnetlu.UUCP> ranson@cnetlu.UUCP (Ranson) writes:
> .
> .When a hard disk is initialized with Apple HD SC Setup using the default
> .partitionning, this program does not seem to use the whole disk! If you
> .look at the detailed description of the partitions, you will find that an
> .extra ("Apple_free") partition is created, that uses about 5% of the disk.
> .
> .Why is it so? One can easily use custom partitionning to get this space
> .back, but are there good reasons not to do it? The lost space is 665K on
> .a 20Mb disk, and probably more on larger disks....
> 
> In my case, my HD20Sc (internal on my SE) had a 917K free partition !  Apple
> was robbing me of almost a megabyte.

Herein lies the clue!  Apple buys disk-drive modules from multiple
vendors;  the disks vary in size somewhat.  Apple's default Mac
partition is set to a size that can fit on all of the "20 meg" drives
that Apple purchases.  The "free" partition fills up the excess space.

There is a real, sane reason behind this apparent madness... Apple is
not doing it to deliberately rook you out of space.  If your disk drive
goes kerBLOOie one of these days, and you take your Mac back to an
Apple dealer for service, the dealer will drop in another Apple "20 meg"
drive.  However, there's no guarantee that this replacement drive will
be made by the same vendor;  its raw capacity may be more than your
original disk's, less, or just the same.

If you have used a backup utility that performs an "image mode"
backup/dump of your Mac file-system, you *MUST* restore it into a
partition of at least equal size.  If you've dumped 21 megs of stuff to
a DC-2000 streaming tape, and then try to restore it into a partition
that's only 20.9 megs in size... well, sorry, Charlie.  You may be
unable to restore the partition (if your backup software sanity-checks
the partition sizes), or you may lose the last part of your last file.
This could be annoying, if you're transporting an image-mode backup of
your public-domain software library to a friend's spare Mac disk;  it
could be disastrous, if you're restoring your only backup copy of vital
corporate data.

You _might_ be lucky, and be able to perform a file-by-file restore of a
dump-tape that was written in image-dump mode.  Then again, you might
not.

So... Apple's software is set up to guarantee compatibility between all
Apple-labelled disks of a specific nominal size.  If you happen to be
fortunate enough to have one of the models that has a somewhat higher
total capacity, then you can repartition your drive and make use of the
extra space.  You may, however, be unable to move all of such a
partition's contents into the corresponding partition on another
Apple-labelled disk of the same nominal size.

The choice is yours.
-- 
Dave Platt    FIDONET:  Dave Platt on 1:204/444        VOICE: (415) 493-8805
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