V7M/man/man4/hk.4

.TH HK 4 
.SH NAME
hk \- RK611/RK06, RK07 moving head disk
.SH DESCRIPTION
The octal representation of the minor device number is encoded
.IR idp ,
where
.IR i
is an interleave flag,
.I d
is a physical drive number,
and
.I p
is a pseudodrive (subsection) within a physical unit.
If
.IR i
is 0,
the origins and sizes of the pseudodisks on each drive,
counted in cylinders of 66 512-byte blocks,
are:
.nf
.PP
	disk	start	length
	0	0	146
	1	146	135
	2	281	129
	3	411	403
	4	0	0
	5	0	0
	6	0	410
	7	0	814
.fi
.PP
If
.IR i
is 1, the minor device consists of the specified
pseudodisk on drives numbered 0 through the designated
drive number. Successively numbered blocks are
distributed across the drives in rotation.
.PP
Systems distributed for these devices
use disk 0 for the root, disk 1 for swapping,
disk 2 for the system sources, and
disk 3 (rk07) or disk 6 (rk06 drive 1)
for a mounted user file system.
Disk 6 (RK06) or disk 7 (RK07) may
be used to create a mounted user
file system, which consists
of an entire disk pack.
Pseudodisks 6 and 7 should not be used
on the system disk pack, because they cover
the entire pack.
.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.
.PP
A `raw' interface
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.'
In raw I/O the buffer must begin on a word boundary.
.SH FILES
/dev/rp?, /dev/rrp?
.br
/dev/hk?, /dev/rhk?
.SH SEE ALSO
/usr/doc/hksizes
.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.