Guide to RAID(Part I/III)

A term coined decades ago, RAID is essentially, disks arranged in a manner to protect the information they contain – simply by adding redundancy.

While there are multiple expansions for RAID – Redundant Array of Inexpensive Disks, which has now transformed to Redundant Array of Independent Disks, the aim is essentially to protect the data and RAID achieves this, by not putting all the data into a single disk.

Performance of storage media, gains a lot of importance in cases where data in the media is to be constantly read from, or written to. Many a time, the bottleneck in a computing environment is related to this input/output performance. Most RAID configurations provide performance enhancement that make it a popular option of SME’s and web-hosts.

Before we go any further, getting familiarized with a few key terms is essential.


It is the process of dividing data into small blocks and spreading these data blocks across several physical disks. Striping is the means by which RAID increases input/output performance, by allowing multiple data reads and writes to work on a single data set at a given point in time.


It is the process of copying data blocks from one disk to one or more additional disks, to make data available from more than one place. In effect it takes snapshot of one disk on to the disk added for redundancy. Mirroring is what makes RAID array fault tolerant.


The concept of parity in computing refers to a technique of checking if data has been lost or written over, when it’s moved from one place in storage to another(or from one computer to another, in case of data transmission).

In the context or RAID, it can be explained with an example. Suppose there are “n” blocks of data, and from these “n” blocks, we compute an extra block of data called the “parity block” and store it separately. The parity block is computed such that even if you lose any of the blocks among the “n” blocks, you could still recreate the missing block from the remaining blocks and the parity block.

The technology of RAID is used in different scenarios, for different end results. The various configurations or implementations are categorized into levels, and are referred to as “Levels of RAID”. More on levels of RAID, their performance, comparison of hardware and software RAID to come. Do keep reading Bobcares Blog!



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