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RP(4)                      Kernel Interfaces Manual                      RP(4)



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 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
            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  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
       file.

       In raw I/O the buffer must begin on a word boundary.

FILES
       /dev/rp?, /dev/rrp?

SEE ALSO
       hp(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.



                                                                         RP(4)