Brief description of RAID

Raid, short for Redundant Arrays of Independent Disks, is cheap in Chinese ※redundant disk array. Disk arrays are also divided into software raid and hardware raid. the soft array is achieved by the software program and the CPU of the computer. because the software program is not a complete system, it can only provide the most basic RAID fault tolerance function. other functions, such as hot backup hard disk settings and remote management, are not recommended. the hardware with independent operations provides the control and computing functions of the entire disk array. it does not rely on the CPU resources of the system.
Since the hard array is a complete system, all required functions can be implemented. therefore, the functions and performance of the hard array are better than those of the soft array. moreover, if you want to make the system a disk array, hard arrays are the only choice. therefore, we can see that the raid Level 5 disk arrays on the market are hard arrays. the soft array is only applicable to RAID 0 and RAID 1. we certainly do not use RAID 0 or raid 1 for the image tower we use for mirroring. As a high-performance storage system, it has been widely used. The level of raid has evolved from the concept of raid to six levels, including 0, 1, 2, 3, 4, and 5. However, the four most common levels are 0, 1, 3, and 5. The following describes the four levels.

RAID 0: combines multiple smaller disks into a large disk, without redundancy, parallel I/O, and the fastest speed. RAID 0 is also called a zone set. It is used to combine multiple disks to form a large hard disk. When storing data, the data is segmented by the number of disks and written into these disks at the same time. Therefore, RAID 0 is the fastest in all levels. However, RAID 0 does not have redundancy. If a disk (physical) is damaged, all data cannot be used.

Raid 1: the two groups of identical disk systems use images for each other, but the speed is not improved. However, an error is allowed for a single disk, with the highest reliability. Raid 1 is an image. The principle is to store data on the primary hard disk and write the same data on the image hard disk. When the primary hard disk (physical) is damaged, the image hard disk replaces the primary hard disk. Because data backup is performed for an image hard disk, RAID 1's data security is the best at all RAID levels. However, the disk utilization is only 50%, which is the lowest utilization of all RAID disks.

RAID 3: RAID 3 stores data in different ways than RAID 0 and RAID 1. RAID 3 uses a hard disk to store data in the ※parity bit. data is stored in segments on other hard disks. It stores data in parallel like RAID 0, but the speed is not faster than RAID 0. If the data disk (physical) is damaged, you only need to replace the bad disk,
The raid Control System reconstructs the data on the new Disk Based on the Data check bit of the disk. However, if the disk (physical) is damaged, all data cannot be used. Although the security of data without images is high, the hard disk utilization is greatly improved by using a separate verification disk, which is n-1.

RAID 5: write data to the disk in the array. The parity data is stored on each disk in the array. An error occurs on a single disk. RAID 5 also ensures data security based on the data check bit. However, it does not store the data check bit on a separate hard disk, but stores the check bit of the Data Segment on each hard disk. In this way, damaged data can be rebuilt based on the check bit on other hard disks. The hard disk usage is n-1.

RAID 0-1: Both RAID 0 and RAID 1 are supported.

Raid 6: The basic structure is the same as that of RAID 5. The difference is that raid 6 has one verification code more than RAID 5. So that 6 can still restore data when two hard disks are broken

For details, refer to: http://buffalo.jp/products/catalog/storage/raid/raid6.html

Raid6 has several algorithms called quasi-raid6, which are not described here.

 

※Redundancy: multiple devices are used to work at the same time. When one of the devices fails, other devices can continue to work. On PC servers, redundancy technology is usually used in disk subsystems and power subsystems.

※Parity bit: sets the parity number through the last parity bit. If the data has an error, you can check it. For details, refer to the address.

Http://zh.wikipedia.org/wiki/%E5%A5%87%E5%81%B6%E6%A0%A1%E9%AA%8C%E4%BD%8D

Brief description of RAID