Chapter 6. Theory of Operation
EK–MOL80–SV. B01
6–33
Drive Defect Management
The RWZ53 drive supports the defect management scheme specified by ISO
10089A and ISO DIS 11560, and ECMA 184. Each DMA consists of a :
•
disk definition structure (DDS)
•
primary defect list (PDL)
•
secondary defect list (SDL)
The DDS contains information on how the disk is organized into user and spare
groups.
There are three important parameters; the variables g, n, and m are used
in the ISO standard, and are used here for consistency:
•
g - number of groups
•
n - number of sectors in a User Group
•
m - number of sectors in a Spare Group
User data is stored initially in the sectors of the User Group, while the Spare
Groups are reserved sectors for the linear replacement sparing algorithm.
The
values of g, n, and m are generally chosen so that they maximize the number of
spare sectors allowed, and maximize the size of the User Area. (The ISO
standard for 650-Mbyte media allows for a maximum of 2048 spare sectors total
from the PDL and the SDL, while the ECMA standard for 1.3 GByte allows for
2057 or 1077, depending on the sector size of 1024 or 512 bytes per sector,
respectively.)
For 1.3 Gbyte, the value for g must be 1 or 16.
In general, for 650-Mbyte: g * (n + m) <= (size of User Area)
In general, for 1.3-GByte: g = 1 or 16, (n, m or n0 through n15 and m0 through
m15 are predefined based on g).
In general, for 2.6-GByte: g = 34 or 30, (n, m, or n0 through n33/29 and m0
through m33/29 are predefined based on g).
For more details consult the ISO or ECMA standard.
The PDL contains a list of defective sector addresses as determined by the
manufacturer or by a certification of the User Area, i.e. during a SCSI Format
Unit Command.
Defective sectors listed in the PDL are managed according to
the slip sparing algorithm described in this chapter.
The SDL contains a list of defective sectors and corresponding replacement
sectors determined during disk use, after certification.
Defect/replacement entries
in the SDL are managed according to the replacement sparing algorithm
described in this chapter.
