Q: Our security systems integrator installed a two-hour UPS for our video servers, but when a 4-hour power failure occurred, the server did not come back on. Why not?
A: There is much more involved in UPS support than physically installing a UPS and plugging the video servers’ power cables into it.
Typically video recording servers are not provided with emergency power, because (until the advent of PoE cameras) emergency power could not easily be provided to cameras during a power outage. It makes no sense to keep the recording system powered up if the cameras are powered down.
However, it can be catastrophic to ignore the impact of a power outage on a video server, because a hard shutdown can corrupt video data. Even if a video server powers back up without any apparent issues, a corrupted video database may fail to properly store, and a significant amount of previously recorded video can be lost.
This is why providing and properly integrating an Uninterruptible Power Supply is critical. A video server with terabytes or petabytes of RAID hard drive storage can be protected with just 10 minutes or so of UPS power—just enough power to allow the video management software, the operating system and the storage expansion servers to shut down in the correct sequence. If the storage expansion servers are powered down before the video server they support, data corruption can result. If there is a network switch between the primary video server and its expansion storage, the switch must remain powered on until both servers have shut down.
Here is a typical shutdown sequence for a video server with an expansion storage unit, to which it communicates via a network switch:
- Video Management Server software. The VMS software should be shut down first, which may involve shutting down one or more VMS components running as operating system services. The VMS has to stop writing to the hard drives before any storage expansion unites can be shut down.
- Server Operating System. Once the VMS has been shut down, the operating system can be shut down.
- Storage Expansion Units. Once the video server operating system has been shut down, storage expansion units can be shut down.
- Network Switch. If there is a network switch between the VMS server and the storage units that switch may now be shut down. Typically, network switches are left running and will either shutdown when the UPS turns off, or remain running throughout the outage.
The startup sequence should work in the reverse order. For example, if the network switch is not running, the server and its storage expansion units can’t communicate. If the VMS tries to record data and the storage expansion unit is not yet running, the VMS will encounter errors writing to the data files and/or database, which may require manual intervention to establish correct operation.
Integrating to the UPS Device
The right kind of UPS device will come with documented software on a disc that can be installed on Windows or Linux servers and used to communicate with the UPS via a network or USB connection. Once the UPS notifies the servers integrated with it that power has been lost, the shutdown sequence should be initiated.
It’s usually very expensive in terms of UPS battery cost to provide the capability to keep many terabytes or more of video hard drives running throughout a power outage. However, with PoE power, it is very feasible to put some of the camera-connected segments of the video network on emergency or backup power, and to enable critical cameras to record to SD memory cards during a power outage. This is easier to do in environments where uninterrupted power is a high requirement, such as in healthcare facilities.
Your video project should always include a Power Plan, and the use of emergency and UPS power should be a part of that plan. If this subject is unfamiliar to you, it’s likely that your IT group will have one or more subject matter experts on power provision for critical IT systems. A security design consultant worth their salt will be able to help you with this as well.