On 23 Apr 2018, at 21:47, Grant Taylor via TUHS <tuhs@minnie.tuhs.org> wrote:
> I had always wondered where Solaris (SunOS) got it's use of the different slices, including the slice that was the entire disk from.
>
> Now I'm guessing Solaris got it from SunOS which got it from 4.x BSD.
>


There is a wonderful Sun cretinism about this. At some recent time (I am not sure how recent but probably mid 2000s), someone worked out that you wanted swap to be at one end of the disk (I think the outside) because on modern disks the data rate changes across the disk and you wanted it at the end with the highest data rate.  But lots of things knew that swap was on s1, the second partition.  So they changed the default installation tool so the slices of the disk were out of order: s1 was the first, s0 the second, s2 was the whole disk (which it already was) and so on.  This was enormously entertaining in a bad way if you made the normal assumption that the slices were in order.  There was also (either then or before) some magic needed such that swapping never touched the first n blocks of the disk where the label and boot blocks were, and it was possible to get this wrong so the machine would happily boot, run but would then fail to boot again, usually at a most inconvenient time.

And the cretinism was that this was mid 2000s:  if you had machine that was paging the answer was to buy more memory not to arrange for faster swap space: it was solving a problem that nobody had any more.