XCPU’s Guide To RAID

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What is RAID?

RAID stands for Redundant Array of Independent Disks but originally meant redundant array of inexpensive disks. It is a umbrella term for a scheme that encompasses many different setups. Basically it is a way of storing the same data in different places (thus, redundantly) on multiple hard drives and by placing data on multiple disks, operations can overlap in a balanced and uniform manner, improving performance considerably. Since multiple disks increases the average time between failures, storing data in a redundant manner also increases fault tolerance.
Now, lets learn a little about the terminology that we’ll be using:

What is “parity”?

Simply put, parity (from the Latin paritas, meaning to be equal or equivalent) refers to a technique of checking whether data has been lost or written over when it’s moved from one place in storage to another or when transmitted between computers.

What is “disk striping”?

Disk striping is the process of dividing a body of data into blocks and spreading the data blocks across several partitions on several hard drives. Each stripe is the size of the smallest partition.

Lets take this into context now, if three partitions are selected with one partition equaling 150MB, another 100MB, and the third 50MB, each stripe will be 50 MB in size.

What is “fault tolerance”?

Fault tolerance is the ability of a component (in this case your hard drives) to withstand the inevitable failure that all computer parts and especially hard drives will see.

What is “ECC”?

ECC stands for error checking and correction.

What is “I/O”?

Quite simply, I/O stands for input/output. It “is the collection of interfaces that different functional units (sub-systems) of an information processing system use to communicate with each other, or the Signal those interfaces. Inputs are the signals received by the unit, and outputs are the signals sent from it.”

What is “XOR”?

Exclusive disjunction, also called exclusive or, and generally symbolized by XOR or EOR, is a logical operation on two operands that results in a logical value of true if and only if exactly one of the operands has a value of true.


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