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    Length: 2751 (0xabf)
    Types: TextFile
    Notes: UNIX file
    Names: »wd.4«

└─⟦26887b7e0⟧ Bits:30009717 Comet 32 harddisk image
    └─⟦28c352965⟧ »/a« UNIX Filesystem
        └─⟦this⟧ »usr/man/man4/wd.4« 

TextFile

.ig
	@(#)wd.4
	@(#)Copyright (C) 1985 by The Institute of Algebraic Meditation
..
.TH WD 4
.SH NAME
wd \- Comet32 Winchester driver interface
.SH DESCRIPTION
.LP
A disk is divided into 8 portions called
.I partitions.
Each partition can be accessed independently via a
special file in /dev.
Files 
.I dc0a
through 
.I dc0h
refer to partitions on disk 0
and files 
.I dc1a
through 
.I dc1h 
to partitions on disk 1.
Partitions can overlap each other, and all need not be present
(these are partitions with size zero).
The disk controller can access two disks.
Normally only disk 1 (system disk) is present.
The genix root file system is always in
.I dc1a
and the swap area always in
.I dc1b.
Disk partitions can be defined to suit each installation using
.IR mkpt (8).
.LP
The block device files listed above 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,
which provides for direct transmission between the disk
and the user's read or write buffer, is also available.
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 begin with an extra 'r'.
.LP
In raw I/O counts must be a multiple of 512 bytes (one page), and the
buffer address must be a multiple on 512 (i.e., be page-aligned).
Attempts to perform I/O
without following these restrictions results in an EIO error.
Likewise
.IR lseek (2)
calls should specify a multiple of 512 bytes.
.LP
.SH FILES
.nf
.ta \w'/usr/include/sys/disk.h'u+(4n)
/dev/dc[0-7][a-h]	block files
/dev/rdc[0-7][a-h]	raw files
/usr/include/sys/disk.h	disk header layout
.fi
.SH DIAGNOSTICS
The driver makes a number of retries on I/O operations before
giving up.
All disk errors are logged and the last few can be 
printed out using
.IR dmesg (8).
.IR Cron (8)
is normally used to do this automatically once every 10 minutes, and
the results are appended to
.I /usr/adm/messages.
This file should be examined (and truncated) periodically
to discover problems with the disk.
The last try on a failed operation is also printed on
the console, and is thus seen immediately.
The message has the form
.sp
disk x error m n [block] (ph=x try=x).
.sp
The meaning of the the error code m n can be found in
Shugart 1610-4 Disk Controller manual,
except for the non\-existent code 1 2 which comes up
regularly and is unexplained (don't worry about it).
The only real solution to a bad block on the disk is to
reformat the disk.  However, 
.IR badsect (8)
can be tried as a temporary solution.
.SH "SEE ALSO"
disk(5), mkpt(8), wdutest(8)
.SH BUGS
The page-alignment restriction for raw I/O should not exist.