Video and data are not created equal

A review of the reasoning behind an iSCSI recording implementation


Most iSCSI vendors, as well as some hard drive and tape drive vendors, run when they hear the word video, due to the 24/7 nature of surveillance. Video is a constant bombardment against the device, not the occasional full, incremental, or differential backup common in data storage. As a result, many vendors will not guarantee their products beyond one year, if they do at all.

Other vendors get snagged on the number of actual iSCSI server sessions they can support. If an iSCSI can only accept 6 to 30 sessions at one time, it is not well suited for a video installation, which typically requires 60 - 256 simultaneous iSCSI server sessions.

The last hurdle vendors fail at is the actual read/write throughput across the backplane of the iSCSI device. The appliance must support more than 200 Mb/s during rebuilds for a video surveillance application.

Overall, be aware that iSCSI is an open standard with mandatory and optional features. Most storage vendors pick a flavor of iSCSI to implement in their devices and test them against the full implementation of a MS, Linux, Open-E, or other initiator. A camera vendor may use all of the mandatory features of the MS initiator but none of the optional features. If the storage appliance wants to see the entire MS iSCSI implementation and does not, communication is impeded or does not take place at all.

I have been to customer sites where the user purchased a lower-end iSCSI model than what was originally recommended in an attempt to reduce costs. The lower-end model either failed at one of the previously mentioned hurdles or used a slightly different implementation of the RFC iSCSI initiator stack, and the customers were unable to record video. Do not assume a different model from the same vendor will work for your system, as it may use a different firmware version or platform than you need.

In summary, it is important to do your homework before making decisions on which video system and which architecture to deploy. Ask questions about the system and how it will affect your network. It is much easier to install the correct system that fits your needs and your network's capabilities, than to rip out the wrong one and start over.

About the author: David Brent is a technical information engineer for IT systems at Bosch Security Systems, Inc. He has extensive knowledge of networks and holds a number of IT and networking certifications. He can be reached at david.brent@us.bosch.com.