VMS provides flexible fail-over options for CCTV systems.

A CCTV system can be designed to minimise data loss and down-time in the event of failure proportional to the critical nature of the site it protects.

VMS provides flexible fail-over options for CCTV systems.

Any CCTV security system can fail. As the video cameras, power supplies, storage devices, servers and network infrastructure in a CCTV system increase, so too does its risk of failure. A well-designed CCTV system must offer a satisfactory solution and response to failure, proportional to the critical nature of a site’s security and operations. In this article, we consider how integrators might use failover options to mitigate the impact of CCTV system failure.

Failover and downtime

The principles of failover are straightforward. If any device in a CCTV system infrastructure fails, the system must firstly recognise the failure has occurred; secondly, automatically trigger a standby device or system to take over; and thirdly, keep downtime to a minimum.

When no failover is in place, the faulty individual parts of a CCTV system will need physically replacing by an engineer. This can be acceptable for non-critical systems where a down-time of a number of days is acceptable. In mission-critical applications, where down-time has to be negligible, procedures must be in place. Failover may demand an entire replacement or “redundant” system to be permanently on “hot standby” to switch on automatically if failure occurs. This level of failover ensures continuity, but requires a duplicate system. It can be expensive, but keeps down-time to a minimum. Between these two extremes, there are some effective failover options, which offer many of the benefits of having a “redundant”, standby system, but at a lower cost.

Digifort VMS offers a robust failover solution

Traditional NVRs use RAID storage to mitigate HDD failure, but NVR failure itself is not addressed. True failover protection for a CCTV system requires a server-based, VMS solution, like Digifort. A VMS solution will minimise down-time and will alert users and engineers to abnormal status in system devices to prevent failure in the first place. Being server-based, VMS solutions are usually more reliable than NVRs. They will support a broad range of failover options for the power, storage, server and network aspects of a CCTV system.

Power failover

Loss of power in a CCTV system is easily addressed using uninterrupted power supplies (UPS). These not only protect against mains spikes, but also allow network devices to shut down cleanly if power is lost. Dual redundant PSUs should be specified in critical applications, so if the primary PSU fails the device or system it powers will continue to operate. Switch over is usually instantaneous and alerts can be configured to email or SMS the system administrator. When the failed PSU is replaced, the spare PSU returns back to redundant operation.

Storage – NAS and RAID redundancy

VMS systems normally use NAS (network attached storage) as the primary means of storing video data. When NAS is deployed using RAID (redundant array of independent disks) and one or more of its HDDs (Hard Disc Drives) fail, video data is automatically routed to the working HDDs. RAID allows hot swapping of failed HDDs, where replacement drives can be fitted to the live NAS and the data on it is rebuilt over time. High quality NAS arrays also feature health checking consoles and configurable alerts.

Digifort supports the failover of the NAS storage arrays themselves. Camera data is re-routed to the designated failover array which, depending on the number of cameras, can occur within 30 seconds.

Internal HDDs, USB/SCSI arrays and some SAN cannot be used for failover, as they do not have an openly available write-path to allow redirection.

Server redundancy

Server failover can be implemented in a number of ways. Digifort will configure servers in a server “farm” using a centralised database for failover communications between the servers and storage. In critical systems, where no failure can be tolerated, 100% server redundancy should be implemented. Each primary server has an allocated “buddy” server on hot standby. This requires a duplication of every server, so is only really suitable for mission-critical applications.

A cost-effective alternative is for a single “buddy” server to be allocated to a farm of live servers. If any one of the primary servers fails, the buddy server is brought into action. Live servers and buddies continuously monitor one another to anticipate problems and reduce the risk of data loss and increase failover response times.

Network design

Network failure is a common issue and if failure occurs in any part of a network, camera communications will usually cease. The network infrastructure itself should be designed with reliability and resilience as key considerations.

There are many ways to design redundancy into a network, but currently a mesh network structure is the simplest and most effective. Multiple routes are available between network switches and CCTV system devices, so if one route fails another is available. Alternatively, “edge” recording cameras will continue to write video data to their built-in memory for synchronisation with Digifort VMS recordings later.

Digifort allows CCTV systems to support failover in all parts of a CCTV system, regardless of the IT Infrastructure. This can reduce the impact of camera, power, storage, server and network failure, ensuring no event is missed.

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