HP(4)							     Kernel Interfaces Manual							     HP(4)

NAME

       hp - RH-11/RP04, RP05, RP06 moving-head disk

DESCRIPTION

       The octal representation of the minor device number is encoded idp, where i is an interleave 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 therefore 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 results.

FILES

       /dev/rp?, /dev/rrp?

SEE ALSO

       rp(4)

BUGS

       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.

																	     HP(4)