DVR and NVR suppliers are reaching out to Western Digital to find fast, reliable and efficient hard drives for their digital video storage solutions. In response, WD has produced the Purple series of drives, designed to meet the specific demands of the CCTV video surveillance market.
Jermaine Campbell, WD Country Manager for the UK, explains that the Purple Drive has been developed in consultation with some of the leading DVR/NVR manufacturers in the security market, who have helped WD understand the specific challenges that hard drives face when used in video surveillance applications.
WD works closely with COP Security, a leading CCTV distributor renowned for its high-quality products and commitment to service and support. COP installs WD Purple drives in all of its DVRs and its smaller network video recorders and uses WD’s Re datacenter capacity HDDs for larger NVRs.
COP Security sells around 10,000 DVRs a year. With some of its units holding up to 24 hard drives, that makes for a whopping 40-50,000 terabytes of HDD storage sold annually.
Some suppliers install inexpensive, unbranded desktop-class hard drives and aren’t very open with their customers about the components that go into their DVRs and NVRs. Gareth Rhodes at COP Security says that unlike those companies, COP has always looked for top quality drives for its DVRs.
In the quest for the best drives, the company has tried a number of manufacturers but found they weren’t reliable enough. “These were desktop drives, designed for a low number of reads and writes in the course of a working day,” he says. “Western Digital has designed a drive specifically for the surveillance industry which is far more reliable.”
One of the big challenges is the typical DVR read/write cycle. Whereas a hard drive in a desktop computer will read a bit of data, write a bit of data and then sit idle, in a DVR the hard drive could be writing data to the disk for more than 90% of the time.
Hard drives are designed to use that idle time to look for bad sectors on the disk. When an error is discovered, the hard drive marks that part of the drive as unusable so it can avoid writing data there. In a surveillance application, a desktop hard drive may hang or freeze, seriously affecting recording.
The Purple drive is different because it uses WD’s AllFrame technology. AllFrame has a unique caching algorithm which significantly reduces the drive’s processor utilization.
In confidential benchmark tests, WD claims to be able to demonstrate that recording the same 16 channels of data, competitors’ drives will be running at 90-100% of drive utilisation while the WD Purple drive will be running at 10-15%.
AllFrame is tailored for the surveillance market by making an important distinction between traditional IT applications and video surveillance applications. In the IT world, you have to ensure that every bit of data is checked to ensure 100% data integrity. If something is missing, the drive will stop and attempt to fix the error.
In video surveillance, in which the data is streaming in continuously, stopping will create an unacceptable backlog in recording which could result in the loss of entire frames.
WD Purple surveillance-class hard drives equipped with AllFrame technology work with ATA streaming to reduce frame loss – key to the surveillance application.
AllFrame also works to reduce interruptions caused by vibrations within the DVR. If you pack two or more hard drives into a DVR, along with fans and other devices, it can lead to an exponential build up of vibrations which can seriously affect the performance of hard drives.
Campbell says that AllFrame analyses the vibrations and then applies compensation to the arm that holds the write head (actuator), keeping it stable. Without Allframe technology these vibrations make it very difficult for the head to stay on track resulting in performance losses.
While some competitors claim to have vibration correction in their hard drives, Campbell claims that “there are degrees of how well that’s implemented”.
The other major innovation of the Purple drive is in the write head itself. As the drive is optimised in favour of writing rather than reading, WD has beefed up the write head to ensure it doesn’t wear out as quickly as a desktop-class hard drive would if it were operating in the same conditions.
WD has very recently introduced a 6TB version of its Purple drive which is proving to be very popular, especially as demand grows for HD and megapixel cameras, says Campbell.
Campbell says he’s delighted to be working with COP Security who have really understood the value and advantages of the Purple Drive.
They work closely together to understand the requirements of the end-users and the demands being placed on hard drives operating within surveillance applications. They also provide training and run open days, and in 2015 you shouldn’t be surprised to see WD and COP Security appearing together at a number of trade shows.
It’s all about educating the market about the importance of specifying the right hard drive for digital video surveillance applications, so that security installers, integrators and customers understand the importance of specifying a hard drive that will withstand the rigours of video surveillance.
The next time you are looking to purchase a digital video recorder, ask the supplier what hard drives are installed in it. If it’s only a desktop-class hard drive, ask yourself if it’s going to be as reliable as the WD Purple drive.
