RAID

A couple of sharp guys in Berkeley back in the 1980s organized the many techniques for using multiple drives for data protection and increasing speeds as the redundant array of independent (or inexpensive) disks (RAID). They outlined seven levels of RAID, numbered 0 through 6.

       An array in the context of RAID refers to a collection of two or more hard drives.

RAID 0-disk striping disk striping requires at least two drives. It does not provide redundancy to data. If anyone drive fails, all data is lost.

RAID 1- disk mirroring/duplexing RAID 1 array require at least two hard drives. Although they also work with any even number of drives. RAID 1 is the ultimate in safety, but you lose storage space because the data is duplicated; you need two 100-GB drives to store 100GB of data.

RAID 2- disk striping with multiple parity drives RAID 2 was a weird RAID idea that never saw practical use. Unused, ignore it.

RAID 3 and 4-disk striping with dedicated parity RAID 3 and 4 combined dedicated data drives with dedicated parity drives. The differences between the two are trivial. Unlike RAID 2, these versions did see some use in the real world but were quickly replaced by RAID 5

RAID 5 –distributed parity instead of dedicated data and parity drives, RAID 5 distributed data parity information evenly acro

Platter based hard drives

A traditional hard disk drive (HDD) is composed of individual disks, or platters, with read/write heads on actuator arms controlled by a servo motor all contained in a sealed case that prevents contamination by outside air.

How hard drives work

Hard drives sport one of two technologies today. The most common type has moving parts; the newer and more expensive technology has none. Let’s look at both.

Of all the hardware on a PC, none gets more attention or gives more anguish than the hard drive. There’s a good reason for this: if the hard drive breaks, you lose data. As you probably know, when the data goes, you have to redo work or restore from backup or worse. It’s good to worry about the data, because the data runs the office, maintains the payrolls, and stores the e-mail. This level of concern is so strong that even the most neophyte PC users are exposed to terms such as IDE, PATA, SATA, and controller even if they don’t put the terms into practice.