V7M/man/man4/hp.4

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.TH HP 4 
.SH NAME
hp \- RH-11/RM02, RP04, RP05, RP06 moving-head disk
   \- RH-70/RM03, RP04, RP05, RP06 moving-head disk
   \- RH-11/ML11 solid state disk
   \- RH-70/ML11 solid state disk
.SH DESCRIPTION
The octal representation of the minor device number is encoded
.IR idp ,
where
.I i
is an interleave flag,
.I d
is a physical drive number,
and
.I p
is a pseudodrive (subsection) within a physical unit.
If
.I i
is 0,
the origins and sizes of the pseudodisks on each drive,
counted in cylinders of 418 512-byte blocks,
for the RP04/5/6 are:
.nf
.PP
	disk	start	length
	0	0	23
	1	23	21
	2	44	21
	3	65	345
	4	65	749
	5	411	403
	6	0	410
	7	0	814
.fi
.PP
The pseudodisks for the RM02/3 are:
.nf
.PP
	disk	start	length
	0	0	60
	1	60	55
	2	115	50
	3	165	657
	4	0	0
	5	0	0
	6	0	0
	7	0	822
.fi
.PP
If
.I 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 souces, and
disk 3 (rp04/5 & rm02/3), or disk 4 (rp06)
for a mounted user file system.
.PP
The ML11 solid state disk may be
connected to the RH11 or RH70 massbus
disk controller in conjunction with
RM and RP disks.
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 RM02/3, RP04/5/6, and ML11 disks
may be attached to a second RH11 or RH70
massbus disk controller at the alternate address
and vector. In this case these disks are
referenced as
.IR hm? .
.
.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/rp?, /dev/rrp?
.br
/dev/hp?, /dev/rhp?
.br
/dev/hm?, /dev/rhm?
.SH SEE ALSO
/usr/doc/hpsizes
.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.
.PP
Raw device drivers don't work on interleaved devices.