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4.5 Performance characteristics
Drive performance is characterized by the following parameters:
Command overhead
Mechanical positioning
- 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”)
4.5.1 Mechanical positioning
4.5.1.1 Average latency
Table 5 Latency Time
Average latency
Rotational speed
Time for a revolution
(ms)
(ms)
7200 RPM
8.3
4.16
4.5.2
Drive ready time
Table 6 Drive ready time
Power on to ready
POR Condition
Typical (sec)
Maximum (sec)
Controlled POR without Deferred FW Activation
25
30
10 Disk model
Controlled POR with Deferred FW Activation
N/A
60
Uncontrolled POR (EPO) with destage to media
cache and possible Deferred FW Activation
N/A
75
Ready
The condition in which the drive can perform a media access command (such as read, write)
immediately
Power on
This includes the time required for the internal self-diagnostics.
Notes: The typical and maximum drive ready times in the table are for proper power shutdown using the required
power-off sequence. The actual time may vary depending on the drive pre-condition before the EPO event.
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Hard Disk Drive Specification