| 1 | .TH RP 4 |
| 2 | .SH NAME |
| 3 | rp \- RP-11/RP03 moving-head disk |
| 4 | .SH DESCRIPTION |
| 5 | The files |
| 6 | .I "rp0 ... rp7" |
| 7 | refer to sections of RP disk drive 0. |
| 8 | The files |
| 9 | .I "rp8 ... rp15" |
| 10 | refer to drive 1 etc. |
| 11 | This allows a large disk to be broken up |
| 12 | into more manageable pieces. |
| 13 | .PP |
| 14 | The origin and size of the pseudo-disks on each drive are |
| 15 | as follows: |
| 16 | .PP |
| 17 | .br |
| 18 | disk start length |
| 19 | .br |
| 20 | 0 0 81000 |
| 21 | .br |
| 22 | 1 0 5000 |
| 23 | .br |
| 24 | 2 5000 2000 |
| 25 | .br |
| 26 | 3 7000 74000 |
| 27 | .br |
| 28 | 4-7 unassigned |
| 29 | .PP |
| 30 | Thus rp0 covers the whole drive, |
| 31 | while rp1, rp2, rp3 can serve usefully as a root, swap, and |
| 32 | mounted user file system respectively. |
| 33 | .PP |
| 34 | The |
| 35 | .I rp |
| 36 | files |
| 37 | access the disk via the system's normal |
| 38 | buffering mechanism |
| 39 | and may be read and written without regard to |
| 40 | physical disk records. |
| 41 | There is also a `raw' interface |
| 42 | which provides for direct transmission between the disk |
| 43 | and the user's read or write buffer. |
| 44 | A single read or write call results in exactly one I/O operation |
| 45 | and therefore raw I/O is considerably more efficient when |
| 46 | many words are transmitted. |
| 47 | The names of the raw RP files |
| 48 | begin with |
| 49 | .I rrp |
| 50 | and end with a number which selects the same disk |
| 51 | section as the corresponding |
| 52 | .I rp |
| 53 | file. |
| 54 | .PP |
| 55 | In raw I/O the buffer must begin on a word boundary. |
| 56 | .SH FILES |
| 57 | /dev/rp?, /dev/rrp? |
| 58 | .SH SEE ALSO |
| 59 | hp(4) |
| 60 | .SH BUGS |
| 61 | In raw I/O |
| 62 | .I read |
| 63 | and |
| 64 | .IR write (2) |
| 65 | truncate file offsets to 512-byte block boundaries, |
| 66 | and |
| 67 | .I write |
| 68 | scribbles on the tail of incomplete blocks. |
| 69 | Thus, |
| 70 | in programs that are likely to access raw devices, |
| 71 | .I read, write |
| 72 | and |
| 73 | .IR lseek (2) |
| 74 | should always deal in 512-byte multiples. |