Raid-array - solving problems with speed of writing / reading and reliability of the system

A raid array is a set of discs that are independent of each other and which are linked together through channels operating at a sufficiently high speed. The system sees this association as one single disk array. The distribution of read and write processes is controlled by the controller.

Raid-array is used to maximize the speed of writing or the reliability of disk storage. Solving the above issues can significantly improve the overall efficiency of the entire system.

Initially, the creation of a RAID array meant combining low-cost disks. This initiative was clearly reflected in the name itself (the abbreviation meant the following: "an excessive array of inexpensive disks"). But later this technology, which proved itself as a quality and reliable, has changed. The modern raid-array is created, as a rule, on the basis of rather expensive equipment. This, in turn, again reflected on the name (today the abbreviation means "redundant array of independent disks").

The development of the information society strongly influenced the requirements that are put forward to the hardware, including information stores. Therefore, since the raid-array was created, several different sub-technologies appeared that were developed to solve specific narrowly-focused tasks.

All the variety of problems solved by computers requires as diverse a variety of technological solutions. Types of raid arrays:

• RAID-0. In the simplest implementation, you need two disks. Incoming information is recorded by blocks in turn on both disks. Reading involves the reverse process. This greatly speeds up the recording, but does not provide sufficient reliability, since an error on one of the disks causes data loss in the entire array.
• RAID-1. In the simplest implementation, you need two disks. The information arriving on the discs is recorded on them in full. This slows down the recording process, but, due to 100% redundancy, it provides a high level of reliability. The main advantage of this development is high fault tolerance and fast reading (since there is the possibility of reading from two disks simultaneously).
• RAID-5. Failover array. In the simplest implementation, you need three disks. Any record of information occurs by splitting the data stream into blocks, each of which is assigned a checksum. In case of data loss on one of the disks, they can be recovered using checksums written on others. Recovery requires the allocation of large capacity, so most often this implementation is used on server hardware.

The raid array of the fifth implementation is the most common. This is due to its reliability and high processing speed , since one array can hold several independent processes of writing and reading simultaneously.