Performance Characteristics; Command Overhead; Figure 8. Performance Characteristics - IBM IC25N040ATCS04 - Travelstar 40 GB Hard Drive Specifications

4.4 Performance 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 contri-
bute 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)
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)

Figure 8. Performance characteristics

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.
Travelstar 60GH & 40GN hard disk drive specifications
60-GB All other models
12
14
5400
5.0
1.0
146-261
100
14
12
14
4200
3.0
1.0
130-245
125-241
100