Intel RAID Controllers - Best Practices white paper

Intel® RAID Controllers Best Practices White Paper

Revision 1.0

7. Enterprise-class versus Desktop-class Drives

Enterprise class hard drives should always be used on an enterprise class system. Use of a

desktop class drive is not recommended due to I/O timeout incompatibilities, lower tolerances

for vibration, and a lack of end-to-end data error detection and correction.

Hard drive manufacturers develop drives to meet specific customer requirements for reliability,

capacity, performance and power consumption. Using drives in the application for which they

were designed ensures your data is available when and how you need it. Using drives outside

of their intended application can negatively impact server productivity.

7.1 Drive Vibration

A hard drive is a non-volatile storage device which typically stores data on rapidly rotating

magnetic platters. Data is usually read and written by a device which is nanometers away from

the surface of the platters. Vibration can significantly affect hard drive reliability and

performance.

There are a number of factors that can cause drives to vibrate, including: vibrations from other

drives or the drive itself, spindle imbalance or torque, and vibration from other system

components such as system fans. These vibrations can cause the read/write heads to misalign

with the data track. When this happens, a retry is required to ensure integrity of the read/write

data. A retry requires milliseconds of time but because drive and storage subsystem electronics

are operating in micro or nanoseconds, a wait of milliseconds can significantly reduce the

overall performance of the storage solution.

Two general categories of drives have evolved to meet customer needs:

 Desktop Drives: These drives perform at an acceptable level when rotational vibration

does not exceed 10 radians per second. They are typically used in single or dual-drive

environments where rotational vibration is limited. A desktop drive is built to have a low

read and write workload over an 8 hour period, 5 days a week. Desktop drives are

designed to work in environments that do not exceed 25 degrees Celsius. As heat

increases, the mean time between failures (MTBF) decreases and the drives are more

likely to fail.

 Enterprise Drives: These drives perform at an acceptable level when rotational

vibration does not exceed 21 radians per second. Enterprise drives are typically used in

multi-drive environments where rotational vibration is normally above 10 radians per

second. The drives are built using advanced technology and components to meet the

performance, workload, and reliability requirements to perform thousands of read/writes

per second, 24 hours a day, 7 days a week. Enterprise drives are also designed for

higher temperatures. The low end of an enterprise drive temperature specification is at

the high end of the desktop specification, making enterprise drives more reliable in

applications where desktop drives fail due to high temperatures. Enterprise drives

usually have a longer warranty period than desktop drives. They often have advanced

power management options. These modes reduce power consumption along with

server cooling requirements, which equate to lower operational costs and less thermal

impact on surrounding system components. Enterprise drives with error recovery control

have the ability to quickly respond with data or to return an error to the host controller.

With a quick response the RAID set is preserved by rebuilding the requested data. Full