Convergence Q&A: Backup Power for Video

A primer on uninterruptible power and orderly shutdown procedures

There can be special considerations involved in deploying Uninterruptible Power Supply (UPS) devices and performing an orderly shutdown upon loss of main power to video system servers.


Q: Why did we still lose all our recorded video when we had a long power outage, even though the video server was connected to our UPS and should have performed an orderly shutdown before the UPS battery was exhausted?


A: The network attached storage was not also on the UPS and so was not protected from instantly being powered off upon the loss of power. Data corruption resulted.


For DVRs, at least partial loss of recorded video upon power outage was common, unless the DVR had UPS battery backup power and the power outages were short enough that the UPS could sustain the machines throughout the outage. Many DVR systems did not have backup power. Unless cameras and any connecting equipment, such as video amplifiers or network switches, can be run off battery backup or emergency power, it makes no sense during a power outage to keep video recording units running whether DVRs, NVRs or servers. There would be no video data to record.

The main concern for the recording units should be to keep them powered long enough to shut them down correctly so that there is no data corruption. Powering cameras from local power sources close to the camera makes UPS backup power for camera infeasible — a UPS at every camera would be cost-prohibitive.

Using toady’s PoE-powered cameras, however, means that keeping the network switches powered automatically keeps the cameras powered. So, where maintaining video monitoring of critical asset areas is crucial — such as healthcare facilities — PoE power can be an affordable solution that enables cameras as well as their recording units to keep functioning throughout a power outage.

For most video systems, emergency power will not be provided during long power outages. Even where emergency backup power is available, if there is even a momentary problem, power system video servers could still lose power. Thus, for nearly all security video deployments, it is important to address UPS backup power and orderly shutdown for video servers and all related components.


Orderly Shutdown and Startup

The simplest scenario for implementing orderly shutdown is a single server computer containing the video storage hard drives, whose backup power comes from a UPS dedicated to that computer. A USB connection from the UPS to the computer provides the data interface, and software provided by the UPS manufacturer can be configured to both perform an orderly shutdown when a main power outage occurs, and ensure that the computer powers up when main power is restored.

Various options exist to allow for an appropriate shutdown sequence, for example: shutting down the VMS application, then shutting down SQL server (for example), then shutting down the operating systems and powering off the machine.

An example of a very complex orderly shutdown scenario is one with multiple video servers, and a UPS shared by IT servers as well as the video servers. The video servers are virtual machine (VM) host computers — each with several virtual machines running various applications, including the main VMS system, video analytics, SQL Server, network monitoring software, VM operating systems and servers, a video storage area network (SAN, where video data is written to) and any network equipment switches and routers that connect video and storage servers.

In a complex system, the shutdown time may be 30 minutes or longer. This may exceed the requirements of other UPS users in the data center, equipment rack or room where the equipment is located.

A UPS is required that supports network-based data connections from multiple computers, not just a one-computer USB connection. Typically such a UPS would support SNMP (Simple Network Monitoring Protocol), which IT would use to monitor the status of the UPS and receive notifications about changes in power status, which could be used to trigger power outage notifications to Security. Vendor-specific protocols also exist, usually for use with vendor-provided UPS management software.

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