Today we come to understand the disk array, the next issue will bring you RAID5, RAID6 configuration practical operation and so on, a lot of cheer.
A, RAID disk arrays Introduction
■ RAID is a Redundant Array of Independent Disks English abbreviation, the Chinese referred to as Redundant Disk Array
■ RAID is to separate a plurality of physical disk combined in different ways to form a disk group (logical drive), thereby providing a higher performance than a single disk storage and backup technology to provide data
■ disk array composed of different ways known as RAID level (RAID Levels), Common RAID levels are as follows: RAIDO, RAID1, RAID5, RAID6, RAID1 + 0, etc.
1. spanned volume (LVM volume)
characteristics: Scalability
Composition Condition: additionally be made of different sizes of disk
capacity: the sum of a plurality of disk capacity
2. striped volume (tape): RAID 0
Characteristics: Write height
disadvantages: unreliable
Composition conditions: the same size disks
capacity: the sum of a plurality of disk capacity
3. mirrored volume: RAID 1
Features: high reliability, a disk may be lost
disadvantages: does not have the scalability
composition conditions: the same size disks
capacity: more than half of the total capacity of the disks
4.RAID 5 volume
characteristics: high reading and writing in general, highly reliable, allowing a damaged disk.
Composition Condition: at least three of the same size disk
capacity: (n-1) / n the total disk capacity
5.RAID 6
Features: ratio compared to RAID5, RAID 6 adds an independent block of the second block of parity information
advantage: even if two disks fail concurrently does not affect the use of data
disadvantages: with respect to a larger RAID 5 "write losses", write performance is poor so
composed conditions: 4 at least the same size as disk
capacity: (N-2) / N capacity 
6.RAID 10 (RAID1 + 0)
characteristics: binding the striped volume (RAID 0) and mirrored (RAID 1), good performance, high reliability, data
composed of conditions: at least four disks simultaneously writes, N disk reading blocks while allowing the disks in the same group of each group a damage, but does not allow the same group in the group while the disk damage.
Second, the array card introduced
1. The function used to implement RAID board, usually composed of I / O processor, a hard disk controller, a hard disk connector and caching of a series of components
2. Different RAID card supports different RAID functionality, such as support for RAID 0, RAID 1, RAID 5 , RAID 10 , etc.
3.RAID card interface type: IDE interfaces, SCSI interfaces, and SAS interface