Version: 2020-09-04
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Job timing
The CS141 provides many system events a job can be assigned to. Some jobs allow to configure advanced timing:
Immediately, once as soon as an event happens, this job is executed at once and not repeated.
After XXX seconds: The CS141 will wait a pre-defined time in seconds and then execute the job. If the event is no
longer active before time is up, the job will not be executed.
Repeat all XXX seconds: The job is repeated cyclically until the event no longer is no longer active.
After XXX seconds on battery: The event forces the UPS will to switch to autonomous mode. The job will be executed if the
UPS remains a pre-defined time in this state. For example, if 300 seconds are set, this job will
only be executed if the UPS operates in autonomous reaches 300 seconds.
At XXX seconds remaining time: The job is executed when the remaining UPS operating time is reached or undershot. Note
based on the current load this time value becomes flexible.
Time management of jobs
The time management of jobs to be performed is difficult since one has to distinguish conceptually between two different points of view.
The following example according to the event power failure illustrates the differences:
In case of a power outage, the UPS will take over power and protect the servers until ...
1. The batteries are depleted
2. Main power is available again
As soon as the UPS runs into autonomous mode, it will start two different timers:
A linearly advancing time in seconds starting at 0.
If a job is to be executed after 45 seconds, it will only be executed if the event is pending for at least 45 seconds. If the event is
terminated before consequently the job is not executed.
A relative clock that counts backwards depending on the connected load currently used.
This becomes tricky if the UPS will operate with a load of 100%
If some of the machines connected to the UPS will be shut down after 3 minutes and cause the load to drop to 50%, it will take effect
this way: Because of dropping load, the clock would jump from 4 minutes to 7.5 minutes.
Both methods to count come with specific advantages and disadvantages:
The first counter gives a clear time window to sequent jobs but ignores the actual remaining time of the UPS:
If there are several small power failures in a row, a server shutdown would not work with a time delay of 5 minutes if battery power is left
to ensure power a maximum of 4 minutes.
The second counter is difficult to calculate and varies depending to the current load. As a consequence, there may be a time lag to
execute configured tasks: 5 minutes remaining time cannot be achieved over a longer period of time, if the circumstances increase the
remaining time - for example some systems will be shut down at 7 minutes remaining time. On the other hand, a predetermined
Sequence of events can get mixed up as soon as the circumstances correct UPS uptime down and cause normally sequentially
configured jobs simultaneously getting triggered.
Note:
Basically, a shutdown using remaining time is useful, since the actually existing battery charge can be included. If a special order must
be observed for jobs, it makes sense to use the linearly forwarding clock for scheduling.
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