4BSD/usr/man/man4/rk.4

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.TH RK 4 
.UC 4
.SH NAME
rk \- RK-11/RK07
.SH DESCRIPTION
Files with minor device numbers 0 through 7
refer to various portions of drive 0,
minor devices 8 through 16 refer to drive 1,
etc.
.PP
The range and size of the pseudo-drives for each drive
are as follows:
.PP
.nf
.ta .5i +\w'000000    'u +\w'000000    'u
RK07 partitions:
	disk	start	length
	0	0	15884
	1	15906	10032
	2	0	53780
	3	0	0
	4	0	0
	5	0	0
	6	26004	27786
	7	0	0
.DT
.fi
.PP
On a dual RK-07 system
partition 0 is used
for the root for one drive
and partition 6 for the /usr file system.
If large jobs are to be run,
partition 1 on both drives provides a 10Mbyte paging area.
Otherwise
partition 2 on the other drive
is used as a single large file system.
.PP
The
.I 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
.I rrk
and end with a number which selects the same disk
as the corresponding
.I rk
file.
.PP
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
.I seek
calls should specify a multiple of 512 bytes.
.SH FILES
/dev/rk?, /dev/rrk?
.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.