General RAID Concept

The important general RAID Concept is physical and logical Arrays and Drives: Before, going into RAID Concepts we should be clear with the fundamental structure of RAID. The fundamental structure of RAID is like an array. An array is nothing but a collection of drives in some definite pattern. The drives are connected in the form of array and the data is split between them to determine the RAID level. The particular definition which are in use is Physical Drives: The Physical Drives are the physical, hard disks that are in the form of the array, Physical Arrays:

The Physical Arrays are physical drives which are connected together to form a physical array. Logical Arrays: The Logical arrays are formed by combining one or more physical arrays. Logical Drives: Logical Drives are formed by connecting one or more logical drivers and are formed from one logical array. The confusing thing is that the terms above, used are similar enough, and are more lightly used. The most RAID consist of one physical array which inturn is made up of one logical array. RAID controllers are like a rope which is needed to hang it comes to defining arrays. Another important RAID Concept is Mirroring: Mirroring is a procedure in which data in the system is written simultaneously to two or more hard disks. Thus it is also known as the mirror concept. The principle of mirroring is to obtain 100% data redundancy, which provides full protection against the failure of either of the disks containing the duplicated data.

The other RAID Concept is Duplexing: Duplexing is an update version of mirroring which is based on the same principle as that mirroring technique. Like in mirroring, all data is duplicated onto two distinct physical hard drives. Duplexing is much more advanced then mirroring in terms of availability because it can provide the data protection against drive failure that mirroring does, but it can also protects against the failure of either of the controllers. The interesting RAID Concept is Striping: Striping is obtained at the byte level, as well as in block level. The Byte-level striping breaks the file into byte-sized pieces. After Byte level striping, the first byte of the file is sent to the first drive, then the second to the second drive, and so on. Block-level striping means that each file is broken into different blocks of a certain size and those are distributed to the various drives.

The last and important RAID Concept is Parity: The parity is used for the system memory error detection. The parity used in RAID is very similar in concept to parity RAM. The principle of parity is simple: take N pieces of data, and compute an extra piece of data. After that take N+1 pieces of data and store it in N+1 drives. If you have lost any one of the data, you can recreate it from the N remain, regardless of which piece is lost. Parity protection is generally used with striping in order to get high performance results across the drives in the array.

The parity information can be stored on a separate, or mixed with the data of drives. The RAID affects important reliability factors such as, For example, a commonly-heard phrase is that RAID improves hard disk reliability, but that is not an true. The truth depends to on how you define reliability and what do you mean reliability of the individual drives, or the whole system.

Data Recovery Software - RAID Recovery

More Information
RAID 0
RAID 1
RAID 1+0
RAID 5
Adaptive RAID
Different RAID Levels
RAID Configuration
RAID Advantages
RAID Reliability Issues
Bad RAID Parity
RAID Concept
RAID Controller
Software Vs Hardware RAID
Quantum DX30 Drives
IBM Servers RAID
IDE RAID Controllers
Fibre Channel
RAID SATA Data Loss
SCSI Interface
Hot Swapping
Storage Controllers
Western Digital RAID Drives
Technical Factors RAID
NAS Servers
Storage Area Network

Related Information
USB Storage Devices
SCSI Tape Drives
Online Data Backup
Project Management
Workflow Software