1.8Data Block Addressing

1.8.1Definition of data space

The IDD manages the data storage area on the disk drive in the following 2 types of data space.

ξUser space: user data storage area

ξSystem space: IDD exclusive area

Within these 2 areas, the user can clearly access the user space. The data format and defect management methods in this space are the same and it is possible to access this space by logical data block addressing described in Section 1.8.2. System space is accessed by the IDD internally when the power is switched on or during processing of specific commands, but it cannot be accessed directly by the user.

Figure 1.5 shows the data space configuration on the disk drive. The number of cylinders allocated to user space can be specified by the user (MODE SELECT or MODE SELECT EXTENDED command).

A spare sector area (alternate area) for use as alternate sectors for defective sectors is allocated in the user space. The IDD manages defects for each cell, which consists of several cylinders (see Figure 1.5). The user can allocate the number of sectors in the last track of each cell and the number of cylinders in the user space (alternate use cylinders) as the alternate area (by the MODE SELECT or MODE SELECT EXTENDED command). Only one cylinder can be specified as an alternate cylinder for the IDD.

Alternate data blocks are allocated in defect sector units for defective sectors on the disk media through internal IDD defect management. Through this defect management, the INIT can access all the logical data blocks in the user space as if they were error free.

For details concerning the data format on the disk media (cylinder configuration, track format and sector format) and details concerning defect management techniques and alternate block allocation techniques, Chapter 3 “Data Format” in the “Product Manual.” For an outline of defect management techniques, see “Disk Media Management” in Chapter 6 of this manual.

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Fujitsu MAN3367, MAN3735, MAN3184 specifications Data Block Addressing Definition of data space
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MAN3735, MAN3184, MAN3367, MAN3735 SERIES DISK DRIVES, MAN3367, MAN3184 specifications

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