Brocade Fabric Watch Administrators Guide (Supporting Fabric OS v7.3.0) - Manual (Page 28)

The figure below shows a high limit of 65° Celsius placed on a counter measuring temperature. During
each sample period, Fabric Watch measures the temperature and compares it to the high threshold. If
the measured temperature exceeds the high threshold, it triggers an event.
FIGURE 3 Time base set to none
Time base set to other than none
If you specify a time base value other than none (minute, hour, or day), Fabric Watch does not use
the current data value. Instead, it calculates the difference between the current data value and the
data value as it existed one time base ago. It compares this difference to the threshold boundary limit.
For example, if you specify the time base minute, Fabric Watch calculates the counter value
difference between two samples a minute apart. It then compares the difference (current data value -
data value one minute ago) against the preset threshold boundary.
When you set a time base to a value other than none, there are two main points to remember when
configuring events:
• Fabric Watch triggers an event only if the difference in the data value exceeds the preset threshold
boundary limit.
• Even if the current data value exceeds the threshold, Fabric Watch does not trigger an event if the
rate of change is below the threshold limit.
The figure below shows a sample graph of data obtained by Fabric Watch (the type of data is
irrelevant to the example). A high threshold of 2 is specified to trigger an event. A time base of minute
is defined. An event occurs only if the rate of change in the specific interval (one minute in this
example) is across the threshold boundary. It should be either higher than the high threshold limit or
lower than the low threshold limit.
As illustrated on the tenth sample, the counter value changes from 0 to 1; thus the calculated rate of
change is 1 per minute. At the thirteenth sample, the rate of change is 2 per minute. The rate of
change must be at least 3 per minute to exceed the event-triggering requirement of 2, which is met on
the eighteenth sample.
Time base set to other than none
28 Fabric Watch Administrators Guide
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