IBM DTNA-22160 - Travelstar 2.1 GB Hard Drive, Технические характеристики

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10.5 Adaptive Power Management Feature
This feature is developed to improve the power consumption and performance in mobile hard drives. This
power management technology intelligently manages power modes within the device by adapting to the indi-
vidual users recent disk access pattern. DTNA-xxxxx support this feature.
This feature has two-stage idle mode. One is Performance Idle mode. The other is Low Power (LP) Idle
mode.
10.5.1 Performance Idle mode
This mode is usually entered immediately after Active mode command processing is complete, instead of
conventional idle mode. In Performance Idle mode, all electronic components remain powered and full fre-
quency servo remains operational. This provides instantaneous response to the next command. The dura-
tion of this mode is intelligently managed as described below.
10.5.2 Low Power (LP) Idle mode
In this mode, power consumption is 15-20% less than conventional idle mode. Additional electronics are
powered off, and the head is parked near the mid-diameter of the disk without servoing. Recovery time to
Active mode is about 40ms.
10.5.3 Transition Time
The transition time is dynamically managed by user's recent access pattern, instead of fixed times. The algo-
rithm monitors the frequency of commands over intervals of interest, usually several seconds. The algorithm
judges how long the current burst of commands will continue by maintaining a distribution of command
frequencies. After each command, the algorithm calculates the probability that the current burst of com-
mands is complete based on the statistics of the distribution.
Each time this algorithm decides that the current burst of commands is not yet complete, it places the device
in Performance Idle mode. This means another command will arrive very soon, and the response to it can
now be instantaneous without the delay associated with conventional idle. Since bursts usually contain tens
of commands, performance is improved.
When this algorithm decides the current burst of commands is complete, it knows with high probability that
the next command will not occur for a relatively long time (seconds). To conserve power, this feature places
the device in LP Idle mode, then performs a seek to the mid-band and enters a low power state.
The optimal time to enter LP Idle is variable depending on the users recent behavior. It is not possible to
achieve the same level of savings with a fixed entry time into LP Idle because each user's data and access
pattern is different. The optimum entry time changes over time.
To recover to Active mode from LP Idle requires about 40 ms. This does not represent a significant per-
formance impact because it is a relatively rare event, and because a new burst of commands almost always
begins with a seek to a new location which requires the time anyway. Throughput is maintained because LP
Idle is entered only when a long idle interval is anticipatied.
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O E M Specifications of DTNA-2xxxx 2.5 inch H D D