Video and data are not created equal

A review of the reasoning behind an iSCSI recording implementation


How Does this Affect the Network?
When you implement IP video, you are paying for three things: inputs, storage, and bandwidth. The three are inseparable, and storage is tied to bandwidth's hip. In the example above, we have a peak network load of 439Mb/s. Most network administrators today have at least a 1 gig production network, so even with the true value of production bandwidth between 70% and 80% (700 to 800 Mb/s); the peak load identified above leaves plenty of room for every day activities, correct? Wait, not so fast!

This peak forecast is for the recorded stream only, and does not include live streams going to PCs, monitor wall applications, or virtual matrix stations. If the airport referenced above has 10 workstations (all in 10 to 15 cameo viewing mode), and three monitor wall applications (each with two flat panels in 5x5 mode), that translates into an additional 366 Mb/s of network consumption. This brings the network usage to 805Mb/s - crippling the 1 gig production network.

So what is the alternative? Decentralize video with iSCSI-based storage. This approach leaves video at the point of its origin - reducing the network load and safeguarding the video against catastrophic loss.

But beware; living on the edge also has its pitfalls.

The Edge and Beyond
The evolution of CCTV encoding over the last decade has been a fast-paced race to the edge. The mindset of most companies in the industry has been to leave the DVR by the wayside, and do the conversion from analog to digital via what is known as the common "edge" encoder.

The encoder is basically the digital signal processor from a DVR grabber card placed in a box with an analog input and an Ethernet jack. This eliminates the multiple layers of failure that typically exist within a big box DVR. Still, most companies rely on the network video recorder (NVR) to do the laborious job of recording. With this old-school mentality, 9 out of 10 companies still place NVRs in the central location where the old DVRs used to reside. While the encoder-plus-NVR combination decentralizes the single point of failure of the DVR, it is the first step in converting from an analog system to digital, and places the burden back on the network when deployed in a centralized fashion.

A better approach pushes encoding to the edge. The emergence of intelligent encoders and IP cameras has enabled these devices to perform motion detection, alarm task scripting, video analytics, e-mail and SMS messaging, and to feature built-in iSCSI initiators. By handling these features at the encoder, you can eliminate the need for a separate PC and its associated acquisition, management and maintenance costs - creating a positive effect on your return on investment.

The last feature in the list above - iSCSI -- is the primary solution for decentralized storage. With true CCTV iSCSI integration, there is little or no operating system intervention, and the encoders or IP cameras can record directly to a target LUN located nearby at the edge or directly connected.

Many vendors tout that they record via iSCSI, but in most cases, it is iSCSI with a catch. Some of the "pseudo iSCSI" solutions on the market are:

  • Recording to an NVR-based system on a Windows Server, and the storage is an iSCSI appliance. This is usually still a centralized approach with iSCSI storage connected to the NVR instead of the typical DAS SCSI storage.
  • iSCSI appliances running a Unix kernel, with the Unix kernel running either ZEN or VMWare with Windows Server installed, and also running an NVR software. This is usually deployed in a centralized fashion and has multiple possible failure points.

The common thread among these pseudo iSCSI solutions is the NVR application. To be truly decentralized, you need to avoid being tied to an NVR anchor. NVR applications are very processor and memory intensive, as they can receive and record video streams from 64 - 128 video sources simultaneously, depending on the vendor implementation.

True iSCSI implementation allows the encoder(s) or IP camera(s) to be assigned to iSCSI target(s). The encoder(s) or IP camera(s) and storage devices do the work - there is no intervening NVR application.

Selecting iSCSI Hardware
There are well over 100 iSCSI vendors in the market today, and each one operates differently. One of the major mistakes I see IT administrators make with CCTV projects is that they insist on using their existing storage appliances. Instead, it is best to ask the CCTV vendor what storage is recommended and why, or what storage devices have been tested with the surveillance equipment.