The primary service, however, that the UPS provides in the case of AC line
problems is extra time. While a UPS can enable the server to continue
operating even if there is a power loss, the primary benefit of a UPS is that the
server software has time to ensure that all caches are written to disk, and to
perform a tidy shutdown of the system.
Some UPSs also offer an automated shutdown and reboot facility for network
operating systems. This is often provided via a serial link to the server and is
commonly known as UPS monitoring.
1.11.1 APC PowerChute
American Power Conversion introduced PowerChute in 1988. PowerChute is
software which interacts with the UPS to provide an orderly shutdown of a server
in the event of an extended AC power failure. PowerChute offers user
notification of impeding shutdown, power event logging, auto-restart upon power
return, and UPS battery conservation features.
The current version is PowerChute Plus V4.2. The PowerChute Plus software
consist of two main components. The first is the UPS monitoring module that
runs as a background process on the server. It communicates with the UPS and
the user interface module, logs data and events, notifies user of impeding
shutdowns, and when necessary, shuts down the operating system.
The second component is the user interface module, which may also be known
as the workstation module. The user interface can run either locally on the
server or over a network on a workstation. It gathers real-time data such as
UPS output, UPS temperature, output frequency, ambient temperature, humidity
and UPS status.
When PowerChute Plus is used with a Smart UPS or Matrix UPS, the
PowerChute monitoring features are augmented by sophisticated diagnostic and
management features. These include:
•Scheduled server shutdowns
•Interactive/scheduled battery logging
•Detailed power quality logging
•Real-time graphical displays showing:
1. Battery voltage
2. Battery capacity
3. UPS load
4. Utility line voltage
5. Runtime remaining

1.11.1.1 Flex Events

Flex Events is a feature of PowerChute Plus. It logs UPS related events which
have occurred and allows for actions to be taken based on these events.
Events can range in severity from informational (not severe) to critical (severe).
For instance, there is an event called

UPS Output Overload

. This event is
considered a critical event and will be generated when the rated load capacity of
the UPS has been exceeded. It is critical because if the situation is not
remedied by unplugging excess equipment from the UPS, the UPS will not
support the load if the power fails.
Chapter 1. IBM PC Server Technologies 53