Go Easy on Your Hard Drives

Factors that can limit video storage system performance


Today’s video surveillance systems have substantial workloads and often operate at all times. With constant operational strain and large amounts of critical data involved, design practices to improve system reliability are always a good investment.

Many modern video surveillance systems rely on hard drives as the storage medium for video capture. Hard drives used in these systems are the only major electro-mechanical element in an otherwise solid-state device; therefore, special consideration should be given to the best practices for hard drive installation into a video surveillance unit.

According to IMS Research, the digital storage capacity of the global surveillance marketplace will reach approximately 3.2 billion gigabytes in the year 2013. With such vast amounts of surveillance data, reliable storage solutions are an absolute necessity.

In addition to choosing a storage product that is designed for its specific workload and data category, it is crucial to implement smart and strategic practices for hard drive integration and operation. By thoroughly evaluating the effects of vibration and shock on the storage system, developing a proper mount design to protect it from such forces and following proper thermal management procedures, you can ensure optimal performance and reliability from your storage solution for years to come.

 

Performance Degradation Due to Vibration and Shock

A hard drive within a surveillance system can experience several types of vibration: translational, which occurs along the x, y or z axis of the drive; multi-axial, which takes place along multiple axes at once; and rotational, a twisting or spinning motion about an axis.

Hard drives are most sensitive to rotational energy that occurs about the motor spin axis (z axis), which is perpendicular to the top cover of the drive. Therefore, rotational vibration (RV) can be a significant issue for hard disk drives, which frequently create this type of energy themselves during operation. Significant reductions in hard drive performance — sometimes more than 50 percent — can result from RV, which is typically generated by the drive’s self-excitations due to seek activity; additional components within the chassis, including other drives, fans or CD-ROMS; and external forces.

The shock environment is described using three primary components: pulse shock, which represents accelerations or displacements; velocity shock, which deals with a sudden change in velocity, as when a falling object hits the ground; and the shock response spectrum, which describes how a system responds to a shock event.

Because shock often disrupts many of the natural frequencies within a storage system, it can cause numerous failures, including permanent deformation, loosened hardware and component-to-component impacts. According to Michael Staiano, an engineer with Seagate Technology, most shock damage to hard drives occurs during installation. Protecting your drive prior to installation and while it is outside the operating environment is paramount to extending the life of the drive and enhancing its reliability.

 

Proper Mounting

Staiano says a best-case mount is typically a rigid mount that holds the drive symmetrically using the side mounting holes, which minimizes RV energy.

Though many consumer digital recording systems use isolation-mount designs for storage integration, surveillance configurations typically work well with more rigid mounts. Isolators are often used to improve acoustics in a video recording infrastructure, but most surveillance systems do not have extensive acoustic needs like those found in consumer digital recording systems.

Hard-mount designs not only hold the disk drive rigid to reduce RV energy, they also provide a more economical means of integrating hard drives into a surveillance configuration. Isolators can be an unnecessary added cost and can actually intensify vibration issues in certain situations.

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