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SCSI/FC disk vs. IDE/ATA disk

Are you comparing SCSI or Fibre Channel disk to IDE or ATA? Expert Chris Poelker lets you know what the disk differences are and what the important metrics are on spec sheets.

Question: Can you please tell me where can I find a document and information that can prove those differences between IDE and SCSI HDD especially the fact that "bearings and the actuator arm mechanics used in the higher priced drives are rated for more useful life than both IDE and ATA"?

Chris Poelker's response:

All you need to do is go to any disk manufacturers Web site and pull down the spec sheets for the individual drives. You can try HGST if you like which will give you information on IBM and Hitachi drives.

One of the important factors you will notice within the spec sheets are the MTB (mean time between failure) ratings for each type of drive. You will find that the ATA type drives, which are built to be placed in PC type environments and therefore priced cheaply, will be rated lower than those built for very high duty cycle environments like RAID arrays. If you look closely at the spec sheets, you will notice different components being used within the drives built for different environments.

The high-end, 2.5 million hour MTBF drives used in high duty cycle environments will cave more exotic components, like "fluid dynamic bearing spindle motors", "acoustic and shock dampers" and AFC media (AntiFerromagnetically Coupled) based on "glass substrate."

The lower cost drives like IDE, ATA, etc. will most likely use less exotic (and less expensive) components and have lower ratings for vibration, temperature, shock and acoustics. You will see MTBF ratings in the 300,000 to 500,000 hour ranges, and lower duty cycles (say 20% rather than 100%). Also look for variations in POH (power on hours) and start/stop cycles. It all comes down to the old adage "you get what you pay for."

This Q&A was in response to this question.

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