Storage systems for video surveillance are getting larger as customers demand more cameras, higher-resolution cameras and longer video-retention times. As a result, security integrators are increasingly faced with the challenge of designing and supporting large-scale video storage that meets the specialized performance, availability and management goals, which are unique to video surveillance. This article walks through the specialized requirements presented by digital video surveillance. It shows how a new form of clustered storage offers enhancements to traditional storage designs that are especially helpful when integrators need to make the jump from small-scale recording systems to large-scale surveillance systems, supporting thousands of cameras and petabytes of storage.

Comparing video data with normal business data

For the purposes of this article, we will talk about two types of data: normal business data and video data. Normal business data consists of email, files, database transactions, and perhaps small graphic images. Video data, by contrast, consists of dense video images that are constantly streaming into the storage system. In both cases, large storage systems deploy the concept of RAID to protect against any disk drive failures in the field. But the way in which these RAID controllers are architected can have a dramatic effect on the performance, cost, and manageability of the systems. Let's look into the characteristics of these two data types since they are markedly different and have large ramifications for storage systems.

Data Set Size: The first characteristic to look at is simply the raw amount of data that needs to be stored. A large database today is roughly 100 gigabytes and only very large companies generate general business data that reaches 1 terabyte (1,000 gigabytes) of information. By contrast, a video surveillance system with just a few hundred cameras can easily generate more than 1 terabyte of stored data in a single day.

Read vs. Write activity: A second characteristic to consider is read versus write activity. Normal business data, whether it is payroll database entries, legal file updates, or email messages generally follows the 80/20 rule, where 80 percent of the time data is being read and only 20 percent of the time is dedicated to write activity. Video data has nearly the exact opposite characteristics with data being written 100 percent of the time and read activity happening only rarely as incidents occur that need to be retrieved and reviewed.