On Mon, Apr 23, 2018 at 4:47 PM, Grant Taylor via TUHS <tuhs@minnie.tuhs.org> wrote:

On 04/23/2018 11:51 AM, Clem Cole wrote:

By the time of 4.X, the RP06 was 'partitioned' into 'rings' (some overlapping). The 'a' partition was root, the 'b' was swap and one fo the others was the rest. Later the 'c' was a short form for copying the entire disk.

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

It was not BSD - it was research. It may have been in 6th, but it was definitely in 7th. Cut/pasted from the V7 PDP-11 rp(4) man page:

NAME

rp − RP-11/RP03 moving-head disk

DESCRIPTION

The files rp0 ... rp7 refer to sections of RP disk drive 0. The files rp8 ... rp15 refer to drive 1 etc. This
allows a large disk to be broken up into more manageable pieces.
The origin and size of the pseudo-disks on each drive are as follows:

disk start length
0 0 81000
1 0 5000
2 5000 2000
3 7000 74000
4-7 unassigned

Thus rp0 covers the whole drive, while rp1, rp2, rp3 can serve usefully as a root, swap, and mounted user
file system respectively.
The rp files access the disk via the system’s normal buffering mechanism and may be read and written
without regard to physical disk records. There is also a ‘raw’ interface which provides for direct transmission
between the disk and the user’s read or write buffer. A single read or write call results in exactly one
I/O operation and therefore raw I/O is considerably more efficient when many words are transmitted. The
names of the raw RP files begin with rrp and end with a number which selects the same disk section as the
corresponding rp file.
In raw I/O the buffer must begin on a word boundary.