NAME

ra − UDA50/RA60, RA80, RA81 winchester disks
rd/rx − RQDX1/RD51/RD52/RD53/RD54 winchester disk and RX50 and RX33 floppy disk
rc − KLESI/RC25 winchester disk

DESCRIPTION

The RA disk driver supports the UDA50 disk controller , used with unibus PDP11 processors, and the RQDX1 Q bus disk controller.  Both of these controllers support the Digital Storage Architecture (DSA) disks via the Mass Storage Control Protocol (MSCP). 

Refer to the ULTRIX-11 System Management Guide for information about logical disk names and disk partition sizes. 

The ra 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. 

RESTRICTIONS

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

FILES

/dev/ra##, /dev/rra##
/dev/rd#, /dev/rrd#
/dev/rx#, /dev/rrx#
/dev/rc#, /dev/rrc#

SEE ALSO

ULTRIX-11 System Management Guide
ULTRIX-11 Software Technical Description