rb.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)rb.4	8.1	9/11/90
.TH rb 4 VAX
.SH Name
rb \- IDC/RL02 disk interface
.SH Syntax
.B "controller idc0 at uba? csr 0175606 vector idcintr"
.br
.B "disk rb0 at idc0 drive 0"
.SH Description
.NXS "rb interface" "RL02 disk interface"
.NXS "rb interface" "IDC disk interface"
.NXR "RL02 disk interface"
.NXR "IDC disk interface"
Files with minor device numbers 0 through 7 refer to various portions
of drive 0;
minor devices 8 through 15 refer to drive 1, and so forth.
The standard device names begin with
.PN rb
followed by
the drive number and then a letter, a through 
h, for partitions 0 through 7.
The question mark (?) character
stands here for a drive number in the range 0 through 7.
.PP
The block files access the disk by the system's normal
buffering mechanism and can 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.
Therefore, raw I/O is considerably more efficient when
many words are transmitted.  The names of the raw files
conventionally begin with an additional letter r, for example,
.PN rrx2c .
.PP
Although RL02 disks have 256-byte sectors,
the driver emulates 512-byte sectors.
Raw I/O counts should be multiples of 512 bytes (a normal disk sector).
In the same way,
.PN seek
calls should specify a multiple of 512 bytes.
.PP
The origin and size (in 512-byte sectors) of the
pseudodisks on each drive are as follows:
.PP
.nf
.ta .5i +\w'000000    'u +\w'000000    'u +\w'000000	'u
RL02 partitions:
.sp 6p
	disk	start	length	cyl
.sp 6p
	rb?a	0	15884	0-397
	rb?b	15884	4520	398-510
	rb?c	0	20480	0-511
	rb?d	15884	4520	398-510
	rb?g	0	20480	0-511
.DT
.fi
.SH Restrictions
In raw I/O, 
.PN read
and
.PN write 
functions truncate file offsets to 512-byte block boundaries;
.PN write
overwrites the tail of incomplete blocks.
Thus, in programs that are likely to access raw devices, 
.MS read 2 ,
.MS write 2 ,
and
.MS lseek 2
should always deal in 512-byte multiples.
.SH Diagnostics
The following messages can appear at the console:
.PP
.B "rb%%d%c: hard error sn%d"
.br
An unrecoverable error occurred during transfer of the
specified sector of the specified disk partition.
Either the error was unrecoverable,
or a large number of retry attempts
(including offset positioning and drive recalibration)
could not recover the error.
Additional register information can be gathered from the system
error log file, 
\f(CW/usr/adm/syserr/syserr.\fI<hostname>\fR.
.PP
.B "rb%d: write protected"
.br
The write protect switch was set on the drive when
a write was attempted.
The write operation is not recoverable.
.PP
.B "idc%d: lost interrupt"
.br
A timer watching the controller detected no interrupt for
an extended period while an operation was outstanding.
This indicates a hardware or software failure.
The error causes a UNIBUS reset and retry of the pending operations.
If the controller continues to lose interrupts, this error will recur
a few seconds later. 
.SH Files
.PN /dev/rb???
.br
.PN /dev/rrb???
.SH See Also
dkio(4), nbuf(4), MAKEDEV(8)