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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)
All the above parameters contribute to drive performance. There are other parameters that contribute to the
performance of the actual system. This specification defines the characteristics of the drive, not the characteristics
of the system throughput which depends on the system and the application.
The terms “Typical” and “Max” are used throughout this specification with the following meanings:
Typical The average of the drive population tested at nominal environmental and voltage conditions.
Max
The maximum value measured on any one drive over the full range of the environmental and voltage
conditions. (See Section 6.2, “Environment” and Section 6.3, “DC Power Requirements”)
Mechanical Positioning
Average Seek Time
(without command overhead, including settling)
Command Type
Typical (ms)
Max (ms)
Read
7.4
10.0
Write
8.2
11.0
Table 5 Average Seek Time
Single Track Seek Time
(without command overhead, including settling)
Common to all models and all seek modes
Function
Typical (ms)
Max (ms)
Read
0.23
0.25
Write
0.32
0.45
Table 6 Single Track Seek Time
Average Latency
Average Latency
Rotational Speed
Time for a Revolution
(ms)
(ms)
7200 RPM
8.33
4.16
Table 7 Latency Time
23
Western Digital Ultrastar DC HC310 SATA Product Manual