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Date:      Sat, 10 May 1997 20:57:31 -0800 (AKDT)
From:      Steve Howe <un_x@anchorage.net>
To:        "Jay D. Nelson" <jdn@qiv.com>
Cc:        freebsd-questions <questions@FreeBSD.ORG>
Subject:   Re: Installation Problems
Message-ID:  <Pine.BSF.3.95q.970510204239.17551B-100000@aak.anchorage.net>
In-Reply-To: <Pine.NEB.3.95.970510142316.3099A-100000@acp.qiv.com>

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On Sat, 10 May 1997, Jay D. Nelson wrote:

> On Sat, 10 May 1997, Steve Howe wrote:
> ->
> ->>         1. Some programs, as mentioned before, still don't work
> ->>            with the slice paradigm and need time to catch up.
> ->
> ->i don't know too much about slices.
> ->can anyone say something about them.
> ->they're probably cool, but i still consider them
> ->non-standard goo.  i assume they exist to partition

ok - i'm remembering some things ...
FBSD must use the same MBR as DOS, and due to the 512 byte space of the
MBR, there is a restiction of 4 partition tables, which are used to load
any of 4 partition entry blocks into memory - which are then used to
bootstrap an OS on that particular partition.

i believe this is all done by the BIOS up to the point of of jumping to
the OS's first instructions - so things must remain DOS compatable up
until the point of the OS taking off (since the BIOS does all the
analyzing of MBR/partition entry blocks), which means the all bootable
filesystems on the drive.

so i would -guess- a slice is just an extra block somewhere in a FBSD
partition that contains data for more "psuedo-partitions" that only FBSD
can deal with.  but i still don't understand why it was so important to
have these extra "psuedo-partitions" at the cost of making things more
non-standard.  i mean - if you really wanted 8 partitions, why not just
get a second hard drive?

/
/dos
/usr
/var

isn't that enough for a 1 drive system?

> Ok, I'll bite. This may or may not be accurate, but it's the way I
> understand the world. In a sense, it is non-standard goo, because it is a
> term used to deal with the brain dead method Micros**t had to deal with
> large drives. DOS (cursed spawn of CPM) is nothing more than what used to
> be called a monitor -- a low level mechanism of dealing with hardware.
> Remember -- it comes from an eight bit world. So what DOS must think of as
> a partition is called a slice in FreeBSD to distinguish the peculiar way
> of hacking a disk DOS uses to overcome address limitations, from a more
> rational method of allocating a disk into filesystems.
> 
> It does have a limitation of 8 per disk.
> 
> -- Jay
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