Alternate Spare Area; Spare Area In Cylinders - Fujitsu MAH3182MC Maintenance Manual

(3) System space
The system space is an area for exclusive use of the IDD itself and the following information are
recorded. The length of the data block is always 512 bytes.
•
Defect list (P list and G list)
•
MODE SELECT parameter (saved value)
•
Statistical information (log data)
•
Controller control information
The above information are duplicated in several different locations for safety.
Note:
The system space is also called SA space.
3.1.2

Alternate spare area

The alternate spare area is provided in the last track of each primary cylinder in the user space, and
in the last track of the cylinder and the alternate cylinder.
The spare area in each cylinder is placed at the end of the last track as shown in Figure 3.2. These
spare sectors are located in the end of the track logically, not necessarily located at the end
physically because of track skew or cylinder skew. (Details are explained on Subsection 3.1.3.)
Size can be specified by the MODE SELECT command.
The number of spare sectors per cylinder can be specified exceeding 32. The default value of
number of 9 space sectors per cylinder is 20.
An alternate cylinder is used when spare sectors in a cylinder are used up or 0 is specified as the
number of spare sectors in a cylinder. 1 cylinder at the end of the user space are allocated as
alternate cylinders as shown in Figure 3.3.
Figure 3.2

Spare area in cylinders

C141-E103-01EN 3 - 5