Hitachi HDS723020BLA642 manual Performance characteristics, Command overhead

7K200 SATA OEM Specification

4.4Performance characteristics

Drive performance is characterized by the following parameters:

Command Overhead

Mechanical Positioning

Seek Time

Latency

Data Transfer Speed

Buffering Operation (Look ahead/Write Cache)

Note: All the above parameters contribute to drive performance. There are other parameters which contribute to the performance of the actual system. This specification defines the essential characteristics of the drive. This specification does not include the system throughput as this is dependent upon the system and the application.

The following table gives a typical value for each parameter. The detailed descriptions are found in section 5.0.

Function
Average Random Seek Time - Read (ms)	10
Average Random Seek Time - Write (ms)	11
Rotational Speed (RPM)	7200
Power-on-to-ready (sec)(Typical)	4.0
Command overhead (ms)	1.0
Disk-buffer data transfer (Mb/s) (max)	876
Buffer-host data transfer (Gbit/s) (max)	1.5/3.0

Table 4. Performance characteristics

4.4.1Command overhead

Command overhead time is defined as the interval from the time that a drive receives a command to the time that the actuator starts its motion.

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