The total is a very big number. The need to store 30GB to 40GB per camera per day isn't unusual. That comes to 1TB or more per camera per month. Now, if a retail organization has 30 to 40 cameras per store and 1,000 stores, you're looking at multipetabytes of storage, even if you're rewriting over some old data (see "Surveillance storage capacity factors," above).
Another challenge is the storage workload. "This is not your typical enterprise storage workload," says Jeff Whitney, VP of marketing at Intransa Inc. For example, surveillance storage is 95% to 98% writing. "It is hard to keep up with a near constant write load," he notes. "The storage system doesn't have any time for the usual housekeeping."
Most SAN storage arrays are optimized for business workloads that use small blocks and present a balance of read/write activity. "With video surveillance, you are constantly writing large sequential blocks," adds Whitney. And you don't keep it long; often just a week, a month, a year at most. And skip the backup; RAID 5 is all the protection that's required.
Finally, video storage has to be simple. The systems are usually deployed and operated by security and facilities people who don't understand storage provisioning and networking. LUNs, zones, masking, RAID--forget it. "You need fast performance to the drive, linear scalability and utterly simple management," says Caswell at Pivot3. That's why DVR/NVR appliances have been such a hit; however, they can't scale in the face of the storage capacities required.
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