RAID (Redundant Array of Inexpensive Disks) is a system developed whereby two or more disks are physically linked together to form a single logical, large capacity storage device that offers a number of advantages over conventional hard disk storage devices:

  • superior performance
  • improved resiliency
  • lower costs

There are a number of RAID levels, each focusing on one or other of these advantages, either singly or in combination. The two principal techniques used are:

  • striping, and
  • mirroring

Striping is the technique to provide increased performance. It is a method of mapping data across the physical drives in an array to create a large virtual drive. The data is subdivided into consecutive segments or stripes that are written sequentially across the drives in the array.

Mirroring was the first real implementation of RAID, typically requiring two individual drives of similar capacity. One drive is the active drive and the secondary drive is the mirror, and the technique provides a simple form of redundancy for data by automatically writing data to the mirror drive when it is written to the active drive.

For many years RAID was the preserve of enterprise, server-based systems. However, in recent years, with many desktop motherboards coming equipped with on-board RAID controllers, the technology has moved to the mainstream, where it is being increasingly deployed both for reasons of extracting the maximum level of performance from a system and as a convenient solution to the issue of data security.

Here, we’re implementing RAID 1 for the purpose of improved resiliency. Hard disk head crashes may be relatively rare in this day and age, but they can still be a catastrophe when they occur. How many people routinely backup their user data? Indeed, with the size of hard disks these days, how practical is it to institute a conventional data backup regime, to tape or removable disk media?

RAID 1 offers a simple and effective solution ……. transparently! In the event of a disk failure, the RAID controller will simply use the mirror drive for data recovery and continue operation. OK, you’ll need to replace the defunct drive to reinstate the former level of resiliency, but you’ll not have lost any of your vital user data!

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