RP(4) Kernel Interfaces Manual RP(4)
rp - RP-11/RP03 moving-head disk
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 bro-
ken 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
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 mecha-
nism 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
In raw I/O the buffer must begin on a word boundary.
In raw I/O read and write(2) truncate file offsets to 512-byte block
boundaries, and write scribbles on the tail of incomplete blocks.
Thus, in programs that are likely to access raw devices, read, write
and lseek(2) should always deal in 512-byte multiples.