RK(IV) 10/15/73 RK(IV)
NAME
rk - RK-11/RK03 (or RK05) disk
DESCRIPTION
Rk? refers to an entire RK03 disk as a single
sequentially-addressed file. Its 256-word blocks are
numbered 0 to 4871.
Drive numbers (minor devices) of eight and larger are
treated specially. Drive 8+x is the x+1 way interleaving of
devices rk0 to rkx. Thus blocks on rk10 are distributed
alternately among rk0, rk1, and rk2.
The rk files discussed above 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 RK files begin with rrk and end with a number which
selects the same disk as the corresponding rk file.
In raw I/O the buffer must begin on a word boundary, and
counts should be a multiple of 512 bytes (a disk block).
Likewise seek calls should specify a multiple of 512 bytes.
FILES
/dev/rk?, /dev/rrk?
BUGS
Care should be taken in using the interleaved files. First,
the same drive should not be accessed simultaneously using
the ordinary name and as part of an interleaved file,
because the same physical blocks have in effect two
different names; this fools the system's buffering strategy.
Second, the combined files cannot be used for swapping or
raw I/O.