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Command Processing
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After this state occurs, the IDD reports the CHECK CONDITION status for all input/output
operation requests except the REQUEST SENSE command. The sense data reported at this time
indicate HARDWARE ERROR [=4] / Internal target failure [=44-nn]. If this state is reported
continuously for input/output operation requests, it is necessary for the INIT to generate a RESET
condition or send a TARGET RESET message and attempt to recover from the error state. For
recommended procedures for error recovery methods by the INIT, see the explanation in Section 5.2
“INIT’s Error Recovery Methods (Recommended).”
1.8 Data Block Addressing
1.8.1 Definition of data space
The IDD manages the data storage area on the disk drive in the following 2 types of data space.
• User space: user data storage area
• System 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 referred by the user (MODE SENSE or MODE SENSE 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 as the alternate area (by
the MODE SELECT or MODE SELECT EXTENDED command). Alternate cylinders for the IDD
cannot be altered by the user.
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.