SCSI Read Capacity Command
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The SCSI Read Capacity command is used to obtain data capacity information from a target device.
The command descriptor block (CDB) structure is:
|0||Operation code = 25h|
The special control fields in the CDB have the following meaning:
- RelAdr - indicates that the logical block address (LBA) value is relative (only used with linked commands).
- PMI - partial medium indicator:
- 0 - return value for the last LBA
- 1 - return value for the last LBA after which a substantial delay in data transfer will be encountered (e.g., the current track or cylinder)
The target will return capacity data structured as follows:
|4–7||Block length in bytes|