Performance Characteristics; Command Overhead; Mechanical Positioning; Table 4: Performance Characteristics - Hitachi IC25N040ATMR04-0 - Travelstar 40GB Laptop Hard Drive 9.5mm 2.5 Inch Notebook HDD Specifications

4.4 Performance characteristics

Drive performance is characterized by the following parameters:

• Command overhead

• Mechanical head positioning
- Seek time
- Latency
• Data transfer speed
• Buffering operation (read ahead/write cache)
Note: All the above parameters contribute to drive performance. There are other parameters that contribute to the
performance of the actual system. This specification tries to define the bare drive characteristics, not system
throughput, which depends on the system and the application.
The following table gives a typical value for each parameter. The detailed descriptions are found in Section 5.0,
"Data integrity" beginning on page 21.

Table 4: Performance characteristics

Function
Average random seek time - read (ms)
Average random seek time - write (ms)
Rotational speed (RPM)
Power-on-to-ready (sec)
Command overhead (ms)
Disk-buffer data transfer (Mb/s)
Buffer-host data transfer (Mb/s)
4.4.1 Command 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

4.4.2 Mechanical positioning

4.4.2.1 Average seek time (including settling)

Table 5: Mechanical positioning performance

Command type
Read
Write
Typical (ms)
12
14
Travelstar 80GN Hard Disk Drive Specification
12
14
4200
3.0
1.0
350
100
Max (ms)
16
17
17