Data Recovery - Presentation of RAID technology

The RAID technology (an acronym for Redundant Array of Inexpensive Disks, sometimes Redundant Array of Independent Disks, translate Ensemble redundant independent disks) can be a storage unit from multiple disks. The unit thus created (called cluster) has a great fault tolerance (high availability), or a greater capacity / writing speed. The distribution of data across multiple disk drives makes it possible to increase the safety and reliability of services.

This technology was developed in 1987 by three researchers (Patterson, Gibson and Katz) at the University of California (Berkeley). Since 1992 it is the RAID Advisory Board, which manages these specifications. It is to form a big disk capacity (and therefore costly) using smaller inexpensive disks (ie including MTBF, Mean Time Between Failure, or the average time between failures is low ).

The discs assembled as RAID technology can be used in different ways, called RAID levels. The University of California has defined 5, which were added levels 0 and 6. Each of them described the way in which data is spread over discs:

* Level 0: called striping
* Level 1: called mirroring, shadowing or duplexing
* Level 2: called striping with parity (obsolete)
* Level 3: called disk array with bit-interleaved data
* Level 4: called disk array with block-interleaved data
* Level 5: called disk array with block-interleaved parity distributed
* Level 6: called disk array with block-interleaved parity distributed

Each of these levels is a way of using the cluster, depending:

* Performance
* Costs
* Disk accesses

DATA Recovery with RAID1

Level 1 is designed to duplicate information to be stored on multiple disks, we talk so mirroring, or shadowing to describe this process.

This provides greater data security, because if one of the disks fails, the data is stored on another, So it can be very useful if you have to recover your Data. On the other hand, reading can be much faster when the two discs are functioning. Finally, given that each disc has its own controller, the server can continue to operate even when one of the disks fails, as well as a truck can continue to run if one of its tires crève because he a number on each axle ...

In return RAID1 technology is very expensive since only half the storage capacity is actually used.