Lead Forensics

Selecting a Server

Specifying a server

So why are we using servers in the first place? For a long time now the basis of most enterprise IP surveillance projects includes the utilisation of many cameras on a sophisticated VMS using a high-powered computer to replace multiple DVR / NVR units. A specialised server with the correct software can record several hundred HD cameras at a good frame rate for several months. What this means is that in a well-designed enterprise system, with a correct server selection, can offer massive advantages in terms of system design and efficiency, power consumption and rack space. Optimised servers for HD surveillance are available now that can process in excess of 4000 Mbps of camera traffic with over a petabyte of on-board useable storage in just 4U – equivalent to over a dozen COTS (Commercial Off the Shelf) servers (or the highest specification NVRs on the market). The power savings alone could pay for the product in just a few years.

The transition from analogue to IP surveillance has been incredibly slow, mainly due to the difference in skill set between the physical security integrator and IT infrastructure specialists. Software and hardware are also completely different disciplines in the IT world which is why to date most VMS suppliers are content with recommending or rebadging COTS IT centric solutions rather than a specialist optimised product. If you are buying an ‘end to end’ solution with an IT centric rebadged server that simply doesn’t fit the bill ask them which server manufacturers they trust and most of them would prefer to recommend an optimised solution rather than losing the sale.

When selecting a server, the three important factors to understand are Throughput, Storage and Resilience and these are discussed in more detail below.


In general industry calculators are poor and often give wildly varied results and partial information. When calculating your server requirements there are two important numbers you need for any h.264 device -Average bandwidth and Peak bandwidth. Average bandwidth is the sum of the individual I and P frames in one second during routine operation measured in Mbps (Megabits per second). This is this number that will be used for storage calculations. Often absent in industry calculators however is the Peak bandwidth value, which is the maximum potential bandwidth output should all pixels be changing at the same time. The server you select must be able to handle the peaks caused by high pixel change on all cameras simultaneously or you risk server failure at potentially the most critical time. On many cameras and VMS’s, a bandwidth cap is applied allowing for an easy calculation but as a rule of thumb peak bandwidth could be four times that of a quiet scene and double that of a busy scene.

As an example of where this calculation is important, think of a hotel. Generally, there will be a few people walking in the corridors at any one time, a few people at the bar and a few at reception with most cameras ticking over on very low bandwidth as pixel change is minimal. Imagine now that there is a fire in the middle of the night, the alarms go off, emergency lighting on, smoke, flames, sprinklers and general chaos. Suddenly all of the cameras will experience very high motion simultaneously and your server must be prepared as this is one of the mission critical applications the CCTV system was installed for in the first place. The last thing you need is the core of your system failing and shutting down when it is needed most.

So, you have done your bandwidth calculations, now what are your options? Most industry available servers are rebadged generalist servers designed for multi-tasking, hosting websites, databases, backup, email servers and likely most of the data on social media sites we all use on a day to day basis and they will also run your VMS if you wish. However, remember there is nothing more data intensive than video other than multiple streams of HD video. Because of their generalist nature IT Centric servers will also often have a restricted throughput seriously limiting the number of HD cameras recording to a single server.

There is a common misconception in the industry that to increase the throughput of a server you simply need to upgrade the processor, however with specialist knowledge and components there are much better ways to optimise throughput. There are a few server manufacturers emerging in the industry today who truly understand how IP video works, who have taken the time to analyse the intricacies and modus operandi of the various VMS options and who are creating servers to meet the demands of increasing camera resolutions without having to make compromises on camera performance. Specialist servers for HD Surveillance are available today with throughputs in excess of 4000Mbps equivalent to over a dozen off the shelf, IT Centric servers commonly on offer.

The VMS you use and other parallel video applications such as Mobile Gateway, LPR or video analytics will all impact the overall performance of your server, often requiring multiple servers or virtualisation to achieve the end requirement. Industry calculators will often only deliver an Average throughput and a storage number, sometimes suggesting a processor that might be required, however they will never provide enough information for your local server manufacturer to build an optimised solution for the application. Consulting an HD Surveillance server specialist can often save considerable time, money, rack space and power not to mention the peace of mind that your hardware solution has been designed with an in-depth knowledge of both IT and IP Video.


Calculating storage correctly is important and asking your server supplier to do the calculations is often the best way to get the optimum results (most specialists in this field would prefer to do this and will guarantee the calculation). Alternatively find a calculator you like that hasn’t let you down, preferably one which errs on the side of caution. Most customers will be delighted if you tweak the cameras up if there is too much storage but the opposite is not true and adding storage retrospectively can be complicated and expensive. Specialist HD surveillance servers are available today with a massive 1,440TB storage before RAID in just 4U. With this many disks higher levels of RAID should be employed so expect to lose 5 or 6 disks to RAID50+mHS (Multiple Hot Spare) or similar leaving around 1,360TB after RAID is applied but don’t forget that this is not the end of the story in terms of calculating actual useable storage. 

Other losses that need to be accounted for include Operating System and Application software (specialist server suppliers will separate these off to separate SSDs in RAID 1 for more efficient operation), Internal Disk firmware (file system, boot data, shadow files and formatting) and Base10 vs Base2 losses (the operating system calculates using Binary and HDDs using Decimal. This means that for example an 8TB disk will show as 8000000000KB / (1024 x 1024 x 1024) = 7.45 TB in Windows). As a rule of thumb allow 10% total losses on the RAW storage after RAID has been applied to be safe.

Resilience, Resilience, Resilience

If you are buying a ‘one replaces many’ product think about the repercussions if the product fails. Most specialist servers built for mission critical applications have multiple resilience levels built in as standard and feature true enterprise class components which have significantly lower failure rates compared with normal commodity components.

The most common part to fail in a server is the hard drive. Surveillance drives are a step up from commodity drives for the budget conscious, however any HDD manufacturer will tell you that if your data is valuable to use true Enterprise drives. A hardware RAID in RAID5 should be the minimum HDD resilience you should be considering for any Enterprise application, however adding an extra redundant disk in the form of RAID5 plus Hot Spare or RAID6 buys you time and additional resilience in the event of HDD failure. Higher storage solutions should employ multiple RAID arrays (such as RAID50 or RAID60 with Hot Spares) which increases performance, reduces RAID rebuilt time and also reduces the statistical probability that a drive failure can break your storage array.

Dual redundant power supplies should be specified as standard and not an optional extra. Whilst reliability and efficiency on PSUs have increased in recent times, this is the second most likely component to fail and will render the entire CCTV system useless unless a backup is in place.

To preserve the integrity of the video archive, drives that run the operating system and VMS application should be separate and mirrored. Another very important part of the server is the quality and resilience of the RAID card which is where the hard work happens. Having battery backup for your RAID card will ensure at least your archive is protected and shuts down correctly in the event of power failure.

Where possible select servers with hot-swap redundant components. This means that failed components can be replaced by someone with little or no IT knowledge without powering the system down.


The server is the single most expensive piece of equipment in an enterprise surveillance system. A well-designed server, that is optimised specifically for IP surveillance, can save time and money. Cutting corners could cost you money and damage your reputation in the long run. If you are dictating to your server supplier what you need for an application you are opening a can of worms? Put the onus on them to recommend, and guarantee, a solution the same as you would with any other specialist CCTV component.

Some questions you may want to ask include; Does your server supplier have a video department? Do they know the intricacies and infrastructure of your selected VMS? Do they have contacts at and work closely with the VMS supplier? Can they do the maths independently? If you present your server supplier with a system design (x cameras, y resolution, z frame rate and v archive) and which VMS you are using, can they design you a solution? If they can’t do it, or if they won’t guarantee their solution will work you have to ask yourself if they are the best partner to support you if things start to go wrong.

Up until recently all industry resources have been dedicated to making higher resolution cameras and software to support these cameras with commercial off the shelf servers being selected to complete the system. The rate of change in IT is exponential compared to the CCTV industry and those that made the jump to IP surveillance will have found that historically compromises have had to be made. Simply replacing a 3-year-old server today with a specialist server designed and optimised for HD surveillance can totally transform an existing IP surveillance solution by reducing compression (improving image quality), increasing frame rates and increasing archives as well as reducing power consumption, cooling requirements and rack space.

As a final thought, recording compressed streams of HD video is only part of the battle, serious consideration should also be given to the hardware requirements to decode and display multiple streams of HD live and playback images, especially given the recent popularity of HD Panoramic cameras. But that is a different article…