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What is the RAID?

In this article I will try to introduce you the RAID. This technology can significantly improve both efficiency and flexibility of access to disk storage.

RAID is the setup of two or more hard disks. This is called the matrix. This solution is used in order to achieve greater safety and efficiency. In this article I will discuss only software RAID. It is slower than the hardware implementation. However, for those of you who do not have a RAID controller or motherboard with built-in RAID can test the capabilities of this technology in a simple and cheap way.

RAID is a generic name of many types (levels) of disk arrays. Below I will discuss the most popular ones.

LINEAR RAID (APPEND)

It creates one large virtual partition from two or more physical partitions. The data are interspersed between the discs (interleaved) or duplicated. This level does not provide the typical benefits of RAID beyond the possibility of creating a partition that is larger than the largest owned disk / partition.

RAID-0 (STRIPPING)

Level 0 is very similar to RAID LINEAR, because the data are written to disk is interleaved across all physical partitions forming part of the matrix. Because the data are stored simultaneously on two or more drives, the writing speed theoretically increases N times (where N is the number of disks in the RAID).

  • Advantages: All drives are seen as one big disk surface being the sum of the surface of the disks in the array. Writing prices is accelerated, but the data read speed is comparable with a single disk.
  • Disadvantages: Lack of resistance to failure drives. If one drive fails, then you will lose the data stored on all disks.

RAID-0 is very well suited as a place to store large media files, since both the transfer of the disk and the record is very fast.

RAID-1 (MIRRORING)

This level of RAID creates an exact copy of the data on one or more additional disks. This improves significantly reliability, because if one of the drives fails, we have a complete copy of the data on the other. If the matrix includes N drives, then the failure of the up to N-1 drives does not cause data loss.

  • Advantages: Increased reliability. In the matrix consisting of 3 discs, the failure of two disks will not damage the array. In certain circumstances, the reading speed of RAID-1 can be compared with the read out of RAID-0 (round-robin).
  • Disadvantages: Decreased write speed. Capacity less than the sum of the capacity of the disks in the array. This means that if you have 3 drives with a capacity of 1 GB, then the combined storage of RAID-1 array is 1 GB.

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