V7M/man/man4/hs.4

.TH HS 4 
.SH NAME
hs \- RH-11/RS03, RS04 fixed-head disk
   \- RH-70/RS03, RS04 fixed-head disk
.SH DESCRIPTION
.PP
The files
.IR "hs0 ... hs7"
refer to
RS03 disk drives 0 through 7.
The files
.IR "hs8 ... hs15"
refer to
RS04 disk drives 0 through 7.
The RS03 drives are each 1024 blocks long and
the RS04 drives are 2048 blocks long.
.PP
The
.IR hs
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 HS files begin with
.IR rhs.
The same minor device considerations
hold for the raw interface as for the normal interface.
In raw I/O the buffer must begin on a word boundary.
.SH FILES
/dev/hs?, /dev/rhs?
.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.