4.3
Performance Characteristics
A file performance is characterized by the following parameters:
y
Command Overhead
y
Mechanical Positioning
• Seek Time
• Latency
y
Data Transfer Speed
y
Buffering Operation (Look ahead/Write cache)
Note: All the above parameters contribute to file performance. There are other parameters that contribute
to the performance of the actual system. This specification tries to define the bare file characteristics, not
the system throughput which will depends on the system and the application.
4.3.1 Command Overhead
Command Overhead is defined as described in the following table.
n/a
0.3
Seek (from Command issue to Seek Start)
0.05
0.01
Write (from Command issue to DRQ)
0.1
0.1
Read (Cache hit) (from Command issue to DRQ)
0.3
0.3
Read (Cache not hit) (from Command issue to
Seek Start)
Time (typical)@queue command
(ms)
Time (typical)
(ms)
Command Type (Files is in quiescence state)
All numerical values are average times.
Figure 3. Command Overhead
4.3.2 Mechanical positioning
4.3.2.1 Average Seek Time (Without Command Overhead, Including Settling)
21.5
20.5
Write (Quiet Seek Mode)
20.5
19.5
Read (Quiet Seek Mode)
10.2
9.2
Write)
9.2
8.2
Read
Maximum
(ms)
Time (Typical)
(ms)
Command Type
Figure
4.
Mechanical Positioning Performance
Deskstar 60 GXP Hard disk drive specification
10
Содержание IC35L020 - Deskstar 20 GB Hard Drive
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