NAME

hp − First  RH11/RH70 massbus disk controller
hm − Second RH11/RH70 massbus disk controller
hj − Third RH11/RH70 massbus disk controller

DESCRIPTION

The HP disk driver supports a heterogeneous mix of up to eight RM02/3/5, RP04/5/6, and ML11 disks on the first RH11/RH70 controller, normally addressed at 0776700.  The HM driver supports an identical mix of disks on the second and third RH11/RH70 controllers, addressed at 0776300 and 0776400 respectively.  The RM03 and RM05 disks may not be used with the RH11 controller because their transfer rates exceed the bandwidth of the unibus. 

Refer to the ULTRIX-11 System Management Guide, Section 1.4 for information about logical disk names and Appendix D for disk partition sizes. 

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:

0.25 mball CPU’s
0.5  mball CPU’s
1.0  mbPDP 11/70 with RH70 only
2.0  mbNO PDP11 CPU’s

The hp and hm files access the disk via the system’s normal buffering mechanism and may be read and written without regard to physical disk records.  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. 

FILES

/dev/hp##, /dev/rhp##
/dev/hm##, /dev/rhm##

SEE ALSO

ULTRIX-11 System Management Guide, Section 2.6 and Appendix A
ULTRIX-11 Software Technical Description

RESTRICTIONS

In raw I/O read and write(2) truncate file offsets to 512-byte block boundaries, and write scribbles on the tail of incomplete blocks.  Thus, in programs that are likely to access raw devices, read, write and lseek(2) should always deal in 512-byte multiples.