124 CHAPTER 8: MANAGING UNINTERRUPTIBLE POWER SUPPLIES
UPS Overview Critical network equipment is often connected to an Uninterruptible
Power Supply (UPS) to ensure continued operation in the event of mains
power loss. A server in a VCX system can be connected to, and can
monitor, one or two (if the server has dual power supplies) UPS devices.
Each UPS includes a battery. The battery maintains a charge while power
is supplied to the VCX system. When power fails, the UPS battery takes
over until its capacity is nearly exhausted. At this point, the connected
VCX system performs a graceful shutdown.
UPS monitoring lets a VCX system know when its UPS is about to run out
of power so that it can shut down. When power returns and the UPS
battery has recharged to a level sufficient to allow another shutdown to
complete, the VCX system restarts automatically.
You can deploy a UPS in either a branch office or regional configuration.
■Branch Offices
In a branch office environment, a UPS supports a VCX branch system
which is typically installed on a single VCX server. Normally, a branch
office does not have support staff on hand to attend to equipment,
and may be unoccupied for long periods of time (nights, weekends,
holidays). Consequently, if the office loses power, it is important that
the VCX system automatically operate on UPS power, shut down
when UPS power is about to run out, and restart when power is
restored.
In this environment, the UPS should only power the VCX system and
any networking equipment (for example a router, switch, or SIP
gateway) in use. The UPS should not be used to power other servers
or devices which require a graceful shutdown because there is no way
to coordinate the shutdown of this other equipment with the VCX
system.
■Regional Offices
In a regional office environment, a VCX system may include multiple
VCX servers, which may share one or more UPS devices. It is also
possible for multiple UPS devices to power individual servers through
use of redundant power supplies.
In this environment, the UPS must power only VCX systems and other
equipment not requiring graceful shutdown.