HGST Ultrastar 7K4000 (SAS) Hard Disk Drive Specification
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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 perfor-
mance of the actual system. This specification tries to define the bare drive characteristics, not system throughput, which
depends on the system and the application.
4.4.1 Mechanical positioning
4.4.1.1 Average seek time (without command overhead, including settling)
Table 6: Mechanical positioning performance
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”)
Command Type Typical (ms) Max (ms)
Read 8.2 10.2
Write 8.2 10.2
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