V7M/man/man4/ml.4

.TH ML 4 
.SH NAME
ml \- RH-11/ML11 solid state disk
   \- RH-70/ML11 solid state disk
.SH DESCRIPTION
.PP
.IR ml?
refers to an entire ML11 unit as a single
sequentially addressed file.
The size of each ML11 unit depends on
the number of array modules installed.
There are 512 512-byte blocks per array module,
for a maximum size of 8192 blocks per unit.
The
.IR ml
disk driver requires that the ML11
be installed on a separate RH11 or RH70
massbus disk controller.
.PP
The ML11 may be used for the swap device
or perhaps mounted on /tmp.
The ML11 has switch-selectable transfer
rates of 0.25 mb, 0.5 mb, 1.0 mb,
and 2.0 mb per second. The following transfer
rate restrictions apply:
.br
.nf

	0.25 mb		all CPU's
	0.5  mb		all CPU's
	1.0  mb		PDP 11/70 with RH70 only
	2.0  mb		NO PDP11 CPU's
.fi
.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,
and raw I/O to an interleaved device is likely to have
disappointing results.
.SH FILES
/dev/ml?, /dev/rml?
.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.