Keeping Your Network Video System Up and Running

Strategies for minimizing scheduled downtime

Like the server component, system storage can benefit from a redundant array of independent drives (RAID), allowing users to easily replace drives in case of failure. Arranging standard, off-the-shelf hard drives so that the operating system sees them as one large logical hard disk increases storage throughput as well as reliability.

There are different levels of RAID — from minimal spares to a full “hot swappable” mirrored solution where there is no disruption to the operation of the system and no loss of data in the event of a hard disk failure.

The two most common RAID levels are:

• RAID-1 (disk mirroring): Information on one disk is duplicated onto one or more disks. This increases the reliability but also increases costs and may reduce performance as data needs to be written on two disks at once.
• RAID-5 (striping with parity): Data and parity are spread over three or more disks and require at least three disks in the array. Read performance is the same as for a single disk; write performance, on the other hand, can be lower as data needs to be written on two disks. RAID-5 can tolerate a single disk failure and still recover all data. Additionally, the disks can be made hot swappable. RAID-5 has become popular because it provides redundancy and maximizes disk space.

Network Cameras
Today’s network cameras include a built-in watchdog that automatically restarts them whenever service is interrupted. But the network camera technology continues to evolve. When you upgrade camera firmware, do the upgrades one unit at a time to avoid creating major blind spots in the surveillance network which would occur if a large batch of cameras were pulled offline at the same time. You can schedule upgrades automatically as a function of the video management software or use vendor-specific tools, such as Axis Camera Management which allows an administrator to control batch upgrades.

Also remember to periodically check that cameras are not redirected, pulled out of focus or covered by post-installation changes to the environment. Many network cameras have the built-in intelligence to automatically alert operators if they have been tampered with.

All electronics require power and sometimes that is the weakest link in the chain. Providing hot swappable power supplies for the servers and switches is one possibility, but if massive power outages are a concern, consider deploying an Uninterruptible Power Supply (UPS) system. Network video systems that use Power over Ethernet, however, have the advantage that the complete surveillance system, including the network cameras, will remain operational for a period of time in a power outage.

What is Acceptable Downtime?
No system has 100-percent availability. In an analog system with VCR recording, for example, the tape needs to be changed every eight hours. During this swap out — albeit for a few brief minutes — no video is being recorded. Statistically, such a set-up delivers an availability of around 99 percent, which is considered very low in the IT industry. Proprietary DVR-based systems also have comparably low availability, often lower than the regular PC servers on which they are based.

Weigh your options. Network-based video surveillance requires a maintenance strategy the same as other network systems. Network cameras need patches and updates just like routers do to improve system functionality and security. Video archives and video management applications need updates the same as database servers and financial record applications.
Circumstances and environment dictate the acceptable downtime window for any particular organization. Educational institutions, for example, would have greater tolerances for scheduling maintenance after-hours. Industrial companies could coordinate their video surveillance system downtime with other system/machinery downtime. Even retailers would have opportunities for downtime after business hours. On the other hand, given their extended hours of operation, the transportation and medical industries face much tighter constraints on when large system maintenance can be performed.

What technologies you choose to deploy to minimize downtime for your video surveillance system will depend on the criticality of coverage and the budget at your disposal to harden the network video system.

Fredrik Nilsson is general manager of Axis Communications, a provider of IP-based network video solutions that include network cameras and servers for surveillance. This story is part of Mr. Nilsson’s “Eye on Video” series appearing in ST&D and on and