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The number of ways to gang
up drives in arrays beyond what has been described (so we will
buy more drives) is amazing. All sorts of RAID X numbers have
And the most honest term that has
come out for some controllers is known as JBOD. This is short
for Just a Bunch Of Disks.
As hard drives spun (compared to floppies) very quickly, the sectors of the track would 'fly past' the read/ write head very quickly. The head could read say, sector 1, and pass the data off to the controller.
Well, even at 3,600 RPM, sector 2 came by really fast. Too fast for the controller to do any more processing. That would mean wait for an entire rotation to complete. Now the controller is waiting around (too long). Solutions require more solutions it would appear.
The solution was called interleaving. By storing the data in sectors such as 3, 6, 9 etc. it gave the controller a chance to catch up. The interleaving could just as well have been in the example, 6, 12, 18 etc. The ratio of these number is known as the interleave ratio. As you may have guessed, the smaller the ratio, the faster the controller has to be, to be able to process the data, and the faster the drive can send and receive data.
Before closing this chapter, a few
loose ends should be covered. This is not so much for the A+ certification
test, but rather the ultimate test of successfully performing in the
Drives are Hot
Today, drives are 1:1 interleave, and are fast, cheap storage. Some might use the slang term, hot. Some drives are literally hot. An old or large drive may burn you if you touch it while in operation.
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CertiGuide to A+ (Core Hardware) (http://www.CertiGuide.com/aplush/) on CertiGuide.com
Version 1.0 - Version Date: December 6, 2004
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