Performance Characteristics; Command Overhead; Figure 11. Performance Characteristics - IBM IC25N020ATDA04 - Travelstar 20 GB Hard Drive Specifications

4.5 Performance characteristics

File 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 file performance. There are other parameters which contri-
bute to the performance of the actual system. This specification defines the essential file characteristics.
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. Detailed descriptions are found in
Section 5.0.
Function
Average Random Seek Time For Read (ms)
Average Random Seek Time For 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 11. Performance characteristics

4.5.1 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 48GH, 30GN & 15GN hard disk drive specifications
48 GB 30 GB
Model Model
12 12
14 14
5400 4200
5.0 3.0
1.0 1.0
135 - 241 125 - 235
100 100
16
15 GB,
20 GB
7.5 GB
Model
Models
12 12
14 14
4200 4200
3.0 3.0
1.0 1.0
121 - 216 125 - 235
100 100
12 GB,
10 GB,
6 GB,
5 GB
Models
12
14
4200
3.0
1.0
105 - 199
100