Savvy security professionals are migrating to digital video solutions in droves, and with good reason: surveillance digital video recorders (SDVR) boast an unprecedented combination of video quality, storage capacity and flexibility, enabling SDVR-based systems to deliver an impressive range of enhanced capabilities:
- Higher image resolution
- More active cameras
- Longer archival periods
- Intelligent video recognition
Abundant storage capacity is a fundamental enabler of such capabilities, and it is here that some video surveillance deployments can go amiss. In an effort to minimise costs, some SDVR systems may utilise multiple low-cost, low-capacity hard disk drives (HDDs) to meet their storage requirements. On its surface, this approach appears to be a viable option to reduce storage expenses.
But initial purchase price is only one part of total cost of ownership, and in other respects this budget-drive approach actually inflates SDVR system costs. Specifically, deploying a plethora of inexpensive desktop-class drives consumes more drive slots, requires more power (while producing more unwanted heat) and significantly reduces system reliability. In many SDVRs there are only a limited number of drive slots available, and budget drives lack sufficient capacity for more and/or higher-quality video streams or longer retention of video data.
The solution? Scale up capacity with a smaller number of large (1TB, 2TB or 3TB) HDDs, purpose-built for surveillance storage duty. The benefits of this approach are both significant and multifold: Compact, more space-efficient SDVR systems can meet the elevated capacity needs of sophisticated surveillance environments, power consumption and failure-inducing heat are both reduced, and cutting the number of drives ensures fewer potential points of failure and thus higher reliability.
The Economies of Scale
Increasing the scale (or capacity) of the drives an SDVR uses while decreasing their quantity pays numerous dividends, both fiscal and physical. As illustrated in the following tables, a single 3TB surveillance drive offers vastly more capacity, consumes much less energy (thus producing far less heat) and delivers greater reliability than SDVR storage that utilises multiple inexpensive desktop-class drives.
An obvious benefit of purpose-built surveillance HDDs derives from their exceptionally high capacities. One 3TB surveillance drive can store 42 days of high-quality video streaming (1280×1024 frame resolution, 30fps, H.264 compressed video). Drop the stream to 704×480 resolution/10fps, and that drive can store a whopping 402 days of video data Greater capacity also enables more video streams to be easily added for broader security coverage. With over six times the capacity of some inexpensive desktop-class drives, a 3TB surveillance drive enables a multitude of video cameras to be deployed, significantly increasing the cost-effectiveness of more compact SDVR systems. For example, a single 3TB drive can store over eight month’s worth of video streams from ten cameras (352×240 resolution/10fps).
Note: The preceding figures and those in the table following reflect H.264 compression; results will vary depending on video compression formats and specific video recording applications used.
Reducing the power consumption of HDDs used in SDVR systems is a key objective for several reasons. Cost savings arising from the fewer watts used by surveillance drives is an obvious benefit, but this greater energy efficiency also results in less heat output. Heat is the enemy of all electronic devices, and reduced drive temperatures ensure that the system runs cooler, enhancing the reliability of both the drives and the SDVR that houses them.
In addition, with surveillance drives imposing less of a thermal load on the SDVR system’s cooling capabilities, SDVR builders are free to employ additional and/or more powerful MPEG encoders and decoders in the system without fear of overtaxing its heat dissipation abilities.
A key external variable affecting both system and HDD longevity is heat. Packing a system with more lower-capacity drives to meet a given capacity level can significantly raise system and drive operating temperatures. And because these budget-priced desktop drives lack application-specific features to address power management, they are more prone to heat-related failures caused by the rigorous duty-cycle and power-on requirements of 24×7 surveillance duty.
More drives in a storage system also mean more potential points of failure. Note that a system’s annualised failure rate (AFR) is additive—the AFR of all drives in the system must be combined to calculate net AFR. Furthermore, the specified AFR of desktop drives is obtained in undemanding 8×5 desktop computing environments and can significantly underestimate the actual AFR such drives will experience in gruelling 24×7 surveillance environments.
Surveillance drives are specifically optimised for digital video security use and thus incorporate advanced power management capabilities. In SDVR systems where massive amounts of information are stored, the large number of drives required can present power consumption challenges when the system starts up. Surveillance drives solve this by drawing less current at startup, which enables the use of smaller power supplies that produce less heat.
Surveillance drives take advantage of energy-conserving features during normal operation as well. Any drive in the system can be spun down into power-saving mode when not in active use. This significantly enhances system cooling efficiency and thus overall system reliability.
In addition to power management capabilities that reduce power consumption and heat generation to improve reliability, purpose-built high-capacity HDDs for surveillance feature optimised firmware to cater specifically to video streaming. ATA-7 streaming commands, along with optimised seek profiles, enable surveillance-ready HDDs to efficiently handle multiple simultaneous video streams without degradation in reliability or performance (commonly seen in utilising standard desktop-class drives).
While deploying a number of inexpensive, low-capacity desktop drives in an SDVR system may seem a tempting way to cut costs, it quickly becomes apparent that this is a false economy. Purpose-built surveillance drives cost only slightly more in terms of GB/dollar than a multitude of desktop-class drives, yet require fewer SDVR drive slots to deliver much higher capacity, consume far less energy and generate less system-threatening heat, all while delivering superior reliability.