Detailed description of the disk array raid

About the disk array raid I believe that everyone is exposed to less, so I have not understood the role of this thing, but it does not matter, today this tutorial provides a detailed introduction of the disk array raid, I hope everyone can Taking time to look at it is very helpful to yourself.

A.Raid Definition

RAID (Redundant Array of Independent Disk) technology was proposed by the University of California at Berkeley in 1987, originally to combine small and inexpensive disks instead of large The expensive disk, while hoping that disk failure will not cause a loss of access to data to develop a certain level of data protection technology. RAID is a redundant array of multiple inexpensive disks that appears as a separate large storage device under the operating system. RAID can take full advantage of the advantages of multiple hard disks, increase the speed of the hard disk, increase the capacity, provide fault-tolerant functions to ensure data security, easy to manage, and continue to work in case of any problem with the hard disk. Affected by a damaged hard drive.

Second, RAID several working modes

1, RAID0

Data Stripping data striping technology. RAID 0 can connect multiple hard drives into a larger capacity disk group, which can improve the performance and throughput of the disk. RAID 0 has no redundancy or error repair capability, and is low in cost. It requires at least two disks, and is generally used only when those data security requirements are not high.

(1), RAID 0 is the easiest way

is to use the same hard disk of x block in the form of hardware through the intelligent disk controller or by using the disk driver in the operating system. Connected together to form a separate logical drive, the capacity is x times that of a single hard disk, and is written to each disk in turn when the computer data is written. When the space of one disk is used up, the data is automatically written to In the next disk, it has the advantage of increasing the capacity of the disk. The speed is the same as the speed of any one of the disks. If any one of the disks fails, the entire system will be destroyed. The reliability is 1/n of the single hard disk.

(2), another way of RAID 0

is to use a block of hard disk to select a reasonable band size to create a band set, it is best to equip each hard disk with a special The disk controller reads and writes data to and from n disks at the same time when the computer data is read or written, and the speed is increased by n times. Improve system performance.

2, RAID 1

RAID 1 is called disk mirroring: mirroring the data of one disk to another, maximizing the reliability of the system without affecting performance. In terms of repairability, it has high data redundancy capability, but the disk utilization rate is 50%, so the cost is the highest, and it is often used in the case of storing critical and important data. RAID 1 has the following characteristics:

(1) Each disk of RAID 1 has a corresponding mirror disk. Whenever data is mirrored synchronously, the system can read from any disk in a mirror disk. data.

(2), the space that the disk can use is only half of the total disk capacity, and the system cost is high.

(3) As long as at least one disk in any pair of mirror disks in the system can be used, the system can operate normally even when there are problems with half of the hard disks.

(4), the RAID system with hard disk failure is no longer reliable, the damaged hard disk should be replaced in time, otherwise the remaining mirror disk will also have problems, then the whole system will crash.

(5) After the replacement of the new disk, the original data will take a long time to synchronize the image, and the external access to the data will not be affected, but the performance of the whole system is degraded.

(6), RAID 1 disk controller load is quite large, with multiple disk controllers can improve data security and availability.

3, RAID0+1

Combine RAID0 and RAID1 technologies, except that the data is distributed on multiple disks, each disk has its physical mirror disk, providing full redundancy. Allows one of the following disk failures without affecting data availability and has fast read/write capabilities. RAID0+1 should create at least 4 hard disks in the tape set in the disk image.