Bandwidth and storage have been major bottlenecks in the implementation of large scale and/or HD/megapixel surveillance projects in the past. Camsecure experienced these issues in 2009 when we installed 150 HDTV surveillance cameras at the Saxon Hotel. This was the first major implementation of Axis cameras and Milestone Software with HDTV cameras and had some major problems that were overcome by using cutting edge technology at the time.
Camsecure has also been very busy redesigning the surveillance system at Sandton City, the largest shopping centre in Africa, over the past two years and is at present busy with upgrades that could bring the total camera count close to 1000. We are going to increase the network efficiency and video retained by three times the original storage time period. Other challenging installations have been in the mining sector where many of the cameras are wireless and powered by solar panels and have added complexities such as monitoring these systems via satellite links.
In this article we will address some critical components of storage that have facilitated us to deliver better quality images, more consistently and over a larger time period to our clients.
Faster disks, more cameras less NVRs
In the design of an NVR (network video recording) solution, the biggest bottleneck thus far has been the read/write speed of the hard drives. The limit of cameras an NVR can record is really determined by the bandwidth from the cameras versus the hard disk performance
As an example, an NVR that can record six HDTV MJPEG Cameras at 12 fps to a SATA Drive should be able to handle the data from 50 HDTV cameras using H.264 compression at the same frame rate, because there is less data from cameras using H.264 compression, more cameras can be recorded.
We also utilise a dual storage system at the Saxon Hotel which means we can use faster more reliable disks for incoming video and then schedule daily transfer of the video footage to cheaper hard drives for long-term storage.
For primary video storage, it is recommended to use faster SCSI drives that are designed for intensive operations. SCSI drives provide:
* 15 000 RPM rotational speeds compared to most SATAs which spin at 7200 RPM. This equates to quicker read/write speeds and up to 50% increased throughput.
* Greater ability to withstand higher rotational vibration interference.
* Lower mean-time-between-failure (MTBF).
* Lower bit error rates (BER).
* Warranties of five or more years.
Redundant disk arrays, bullet proof storage
What do you do when a hard drive fails on your recording server; Murphy’s Law dictates that this will happen at the most inappropriate time. To safeguard against losing recorded footage at the Saxon Hotel and other sites, Camsecure used redundant disk arrays which meant that we could have a disk failure and not lose any footage. By using Raid 5 or Raid 6 disk arrays we can lose one or two disks respectively, without influencing the recorded footage. This is great for assuring that the video footage is kept safely for long-term storage.
By implementing Raid configuration on our fast disks for the primary recordings we can increase the read/write performance and have some redundancy with regards to disk loss as well.
For more information contact Camsecure, +27 (0)11 781 1341, firstname.lastname@example.org
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