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 treat-
ed specially. Drive 8+x is the x+1 way interleaving of de-
vices rk0 to rkx. Thus blocks on rk10 are distributed al-
ternately among rk0, rk1, and rk2.
The rk files discussed above access the disk via the sys-
tem'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 be-
tween the disk and the user's read or write buffer. A sin-
gle 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, be-
cause 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.
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