06-18-2013
It is the same measurement as in "iostat". There is a sensor inside the OS for every hdisk device. This sensor either shows "busy", when the command queue of the disk is non-empty, or "idle", if it is. This sensor is queried several times per second (i have forgotten the exact rate). Then, a percentage is calculated by matching the number of "idle" answers to the number of "busy" answers.
It is in the nature of this measurement that many very small disk requests can saturate the comman buffer and make a disk "100% busy" when it effectively doesn't do that much. This does not necessarily mean the disk is at its limit, just that the command queue has never been empty. Correlate this with the I/O amount ("kb_read" and "kb_written") to get a picture about how much stress the disk is effectively exposed to.
I hope this helps.
bakunin
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LEARN ABOUT DEBIAN
sensors
Sensor Classes(3) Coin Sensor Classes(3)
NAME
Sensor Classes -
Classes
class SoAlarmSensor
The SoAlarmSensor class is a sensor which will trigger once at a specified time.
SoAlarmSensor provides a convenient way of setting up triggers for jobs which should be executed only once when they are scheduled. "
class SoDataSensor
The SoDataSensor class is the abstract base class for sensors monitoring changes in a scene graph.
If you need to know when a particular entity (as a field or a node) changes, subclasses of SoDataSensor can be used to monitor the entity
and notify you when it changes. "
class SoDelayQueueSensor
The SoDelayQueueSensor class is the abstract base class for priority scheduled sensors.
Delay queue sensors are invoked upon various events not related to time occurrences. See documentation of subclasses to see which types of
events can be surveilled by the builtin sensor types. "
class SoFieldSensor
The SoFieldSensor class detects changes to a field.
Attach a field to a sensor of this type to put it under surveillance, so you can act upon changes to the field. "
class SoIdleSensor
The SoIdleSensor class is a sensor which will trigger as soon as the application is idle.
An SoIdleSensor differs from an SoOneShotSensor in that it will not trigger if the delay queue processing is occurring due to the delay
queue timeout, but only when the application is idle. "
class SoNodeSensor
The SoNodeSensor class detects changes to nodes.
Attach a node to a sensor of this type to put it under surveillance, so you can act upon changes to the node. "
class SoOneShotSensor
The SoOneShotSensor class is a sensor which will trigger once.
Since SoOneShotSensor is a subclass of SoDelayQueueSensor, it will trigger as soon as either the run-time system is idle, or if it is
continually busy it will trigger within a fixed amount of time (this is by default 1/12th of a second, see
SoSensorManager::setDelaySensorTimeout()). "
class SoPathSensor
The SoPathSensor class detects changes to paths.
If you need to know when a path changes (i.e. nodes in the path has been removed, or new nodes is added), use this sensor to get a
notification. "
class SoSensor
The SoSensor class is the abstract base class for all sensors.
Sensors is a mechanism in Coin for scheduling jobs to be run upon specific events. The events in question could be particular points in
time, or changes to entities in the scene graph. "
class SoSensorManager
The SoSensorManager class handles the sensor queues.
There are two major sensor types in Coin, 'delay' sensors and 'timer' sensors: "
class SoTimerQueueSensor
The SoTimerQueueSensor class is the abstract base class for sensors triggering on certain timer events.
Timer sensors triggers upon specific points in time. "
class SoTimerSensor
The SoTimerSensor class is a sensor which will trigger at given intervals.
Use sensors of this class when you want a job repeated at a certain interval, without explicitly needing to reschedule the sensor (i.e.
SoTimerSensor automatically re-schedules itself after it has been triggered). "
Detailed Description
Sensors are objects that monitor other objects for changes and invoke callbacks when changes occur.
Author
Generated automatically by Doxygen for Coin from the source code.
Version 3.1.3 Wed May 23 2012 Sensor Classes(3)