Data Format
3.1.5Format capacity
The size of the usable area for storing user data on the IDD (format capacity) varies according to the logical data block or the size of the spare sector area. Table 3.1 lists examples of the format capacity when the typical logical data block length and the default spare area are used. The following is the general formula to calculate the format capacity.
[Number of sectors of each zone] = [number of sectors per track ⋅ number of tracks per cell – number of alternate spare sectors per cell] ⋅ [number of cells in the zone]
[Formatted capacity] = [total of sectors of all zones] ⎟ [number of physical sectors in logical block] ⋅ [logical data block length]
The following formula must be used when the number of logical data blocks are specified with the parameter in the MODE SELECT or MODE SELECT EXTENDED command.
[Format capacity] = [logical data block length] ⋅ [number of logical data blocks]
The logical data block length, the maximum logical block address, and the number of the logical data blocks can be read out by a READ CAPACITY, MODE SENSE, or MODE SENSE EXTENDED command after initializing the disk medium.
| Table 3.1 | Format capacity |
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Model | Data block length |
| User blocks | Format capacity (GB) |
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MAY2073RC | 512 |
| 143,638,992 | 73.5 (*) |
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MAY2036RC |
| 71,819,496 | 36.7 (*) | |
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(*) 1 GB = 1,000,000,000 bytes
Note:
Total number of spare sectors is calculated by adding the number of spare sectors in each primary cylinder and the number of sectors in the alternate cylinders.
3.2Logical Data Block Addressing
Independently of the physical structure of the disk drive, the HDDs adopt the logical data block addressing as a data access method on the disk medium. The HDDs relate a logical data block address to each physical sector at formatting. Data on the disk medium is accessed in logical data block units. The INIT specifies the data to be accessed using the logical data block address of that data.
The logical data block addressing is a function whereby individual data blocks are given addresses of serial hexadecimal numbers in each drive.
