Origin of "partition" in storage devices

[Warner Losh]

On Mon, Jan 31, 2022, 2:43 PM Noel Chiappa via cctalk <cctalk at classiccmp.org>
wrote:

>     > From: Paul Koning
>
>     > When did Unix first get partitions?
>
> 'Partitions' the mechanism, or partitions the term for the mechanism?
>
> The former appeared about V5:
>
>   https://minnie.tuhs.org/cgi-bin/utree.pl?file=V5/usr/sys/dmr/rp.c
>
> when an RP03 was added; pre-V7, UNIX filesystems were limited to 2^16
> blocks,
> so the 406*10*20 blocks of an RP03 had to be split up into partitions
> (called
> 'sections' or 'pseudo-disks' in the documentation) to make all of it
> useable.
>
> The latter? No idea...
>

SunOS 1.0 had on disk tables that described the partitions in 1982. These
were dynamic per disk as opposed to the hardwired in the os drivers that V5
and later had. I've not had luck with finding people to recall where this
feature came from...

Partitions may have appeared in DOS/Windows for much the same reason; with
> 32
> KB clusters, FAT16 filesystems were limited to 2GB. I distinctly recall
> having to use partitions when I bought a 13GB hard drive for my Windows 95
> machine (FAT32 only came in with Windows 95 OSR2).
>

There were similar tables on DEC Rainbow disks which predated the MS DOS
port to the platform and was a different format. This was also 1981 or
1982. 3rd party disks had their own tables. I've not done the deep dive to
date it more specifically. Other CP/M raw disks from this era have similar
tables on them, but I have only what I've puzzled out, no docs.

Warner

>