BAD144(5) BSD Programmer's Manual BAD144(5)NAMEbad144 - DEC STD 144 bad block format
SYNOPSIS
#include <sys/types.h>
#include <sys/dkbad.h>
DESCRIPTION
The bad144 format is used by some disk drivers to provide replacement
sectors for faulty areas on a drive. Such drivers include the wd(4)
driver on Intel (R) systems and the hk(4) and hp(4) drivers on VAX (R)
systems.
The bad sector information is located in the first 5 even numbered sec-
tors of the last track of the disk pack. There are five identical copies
of the information, described by the dkbad structure.
Replacement sectors are allocated starting with the first sector before
the bad sector information and working backwards towards the beginning of
the disk. A maximum of 126 bad sectors are supported. The position of
the bad sector in the bad sector table determines the replacement sector
to which it corresponds. The bad sectors must be listed in ascending or-
der.
The bad sector information and replacement sectors are conventionally on-
ly accessible through the ``c'' file system partition of the disk. If
that partition is used for a file system, the user is responsible for
making sure that it does not overlap the bad sector information or any
replacement sectors. Thus, one track plus 126 sectors must be reserved
to allow use of all of the possible bad sector replacements.
The bad sector structure is as follows:
struct dkbad {
long bt_csn; /* cartridge serial number */
u_short bt_mbz; /* unused; should be 0 */
u_short bt_flag; /* -1 => alignment cartridge */
struct bt_bad {
u_short bt_cyl; /* bad sector cylinder number */
u_short bt_trksec; /* track and sector number */
} bt_bad[126];
};
Unused slots in the bt_bad array are filled with all bits set, a puta-
tively illegal value.
SEE ALSOdiskdefect(8)BSDI BSD/OS April 2, 1995 1