Do you know what a RAID array is?

The reliability of data storage is one of the most important and topical issues in computer systems. Therefore, a lot of efforts and developments were concentrated in this direction, and as a result, a technology for building RAID arrays appeared, which, despite the fact that it was invented several years ago, is quite relevant and in demand at the moment.

Let's try to figure out what kind of technology it is. To begin with, it is necessary to define the main term. So, a RAID array is a sort of redundant set of independent disks that serve to increase the fault tolerance and efficiency of computer systems. The first is achieved precisely because of redundancy, and the second is due to the simultaneous operation of disks that are in the created array. It's worth noting that the RAID array is used as a single disk by the interaction of software and hardware.

To answer the question of how to create a RAID array, it is necessary to mention that there are several different variations (levels), the implementation of which depends on the organization of the work of the disks. The general operation of disks can be organized using either parallel or independent access. In the first case, to record information, disk space is divided into strips (blocks), which then fall on different physical disks (the performance is enhanced by the simultaneous recording of strips). When reading information, all operations also pass in blocks, which contributes to an even greater increase in the efficiency of such a system. Moreover, the more disks, the more productive the RAID array will be. But there are also some nuances. It is impossible to organize such a system if the block size is larger than the size of the information recording request itself.

In the case of independent access, all the information of a single user request is written in the same way as when working with one logical disk, but unlike the latter situation, read operations will already be performed on different (separate) disks.

At this point in time, there are several standard ways to organize (levels) a system such as a RAID array. They are numbered from 0 to 6 and are called, respectively, RAID 0, RAID 1 and so on. In practice, the most commonly used levels are: 0, 1, 3, and also 5.

So, in order to practically implement an external RAID array, you need to have two components: a RAID controller that performs the functions of distributing incoming information, communicating with the main server, generating redundant data, and any array of hard drives. This is the so-called hardware variant of creating a RAID array. But this is not the only way to organize disks. The construction of such a system is possible from the so-called software environment. In this variant, the creation of RAID arrays is carried out with the help of special utilities, which are supported by this or that operating system. The disadvantage of this implementation is that if the PC software fails, all the information stored on the logical RAID disks will be lost. In addition, we must remember that you can programmatically build an array of only the first and zero level.