.TH UP 4 .SH NAME up \- emulex sc21/ampex 9300 UNIBUS moving head disk .SH DESCRIPTION Files with minor device numbers 0 through 7 refer to various portions of drive 0; minor devices 8 through 15 refer to drive 1, etc. .PP The origin and size of the pseudo-disks on each drive are as follows: .PP .ta .5i +\w'000000 'u +\w'000000 'u .nf 9300 partitions disk start byte 0 0 15884 1 16416 33440 2 0 500992 3 341696 15884 4 358112 55936 5 414048 36944 6 341696 159296 7 49856 291346 .DT .fi .PP 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. 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 files conventionally begin with an extra `r.' .SH FILES .ta 2i /dev/up[0-3][a-h] block files .br /dev/rup[0-3][a-h] raw files .SH SEE ALSO rp(4) .SH BUGS In raw I/O .I read and .IR write (2) truncate file offsets to 512-byte block boundaries, and .I write scribbles on the tail of incomplete blocks. Thus, in programs that are likely to access raw devices, .I read, write and .IR lseek (2) should always deal in 512-byte multiples.