hp - RH-11/RP04, RP05, RP06 moving-head disk
The octal representation of the minor device number is encoded idp, where i is an inter-
leave flag, d is a physical drive number, and p is a pseudodrive (subsection) within a
physical unit. If i is 0, the origins and sizes of the pseudodisks on each drive, counted
in cylinders of 418 512-byte blocks, are:
disk start length
0 0 23
1 23 21
2 0 0
3 0 0
4 44 386
5 430 385
6 44 367
7 44 771
If i is 1, the minor device consists of the specified pseudodisk on drives numbered 0
through the designated drive number. Successively numbered blocks are distributed across
the drives in rotation.
Systems distributed for these devices use disk 0 for the root, disk 1 for swapping, and
disk 4 (RP04/5) or disk 7 (RP06) for a mounted user file system.
The block files access the disk via the system's normal buffering mechanism and may be
read and written without regard to physical disk records.
A `raw' interface 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 there-
fore raw I/O is considerably more efficient when many words are transmitted. The names of
the raw files conventionally begin with an extra `r.' In raw I/O the buffer must begin on
a word boundary, and raw I/O to an interleaved device is likely to have disappointing
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.
Raw device drivers don't work on interleaved devices.