[TUHS] /dev/drum

[Dan Mick]

On 04/23/2018 02:06 PM, Clem Cole wrote:
> 
> 
> On Mon, Apr 23, 2018 at 4:47 PM, Grant Taylor via TUHS
> <tuhs at minnie.tuhs.org <mailto:tuhs at 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.​
> 
> ᐧ

But...that has numbers, not letters, and the third partition is not the
whole drive, the first one is....?