RAID technology,

RAID technology,
A disk array (RAID) is a Redundant Array composed of Independent Disks. A disk array is a combination of many Inexpensive Disks into a disk group with a large capacity. The addition effect produced by the data provided by individual disks improves the efficiency of the entire disk system. This technology is used to cut data into multiple segments and store them on each hard disk. [1] The disk array can also use the concept of Parity Check to read data when any hard disk in the array fails. During data restructuring, after calculation, the data is re-inserted into the new hard disk. There are three types of Disk Arrays: External disk array, internal disk array, and software simulation. External disk array cabinets are most often used on large servers, with Hot Swap features, but these products are expensive. The internal disk array card is suitable for technical staff because it is cheap but requires high installation technology. The hardware array provides functions such as online resizing, dynamic modification of the array level, automatic data recovery, drive roaming, and ultra-high speed buffering. It provides performance, data protection, reliability, availability, and manageability solutions. A special processing unit for the array card. By means of software simulation, multiple hard disks connected to the common scsicard are configured as logical disks through the disk management function provided by the network operating system to form an array. The software array can provide data redundancy, but the performance of the disk subsystem may be reduced. Some software Arrays can reduce the performance by about 30%. This will drag down the speed of the machine and will not fit the server with big data traffic. Principle disk arrays act as independent systems directly connected to hosts outside the host or connected to hosts through the network. The disk array has multiple ports that can be connected by different hosts or ports. A host connects to different ports of the array to increase transmission speed. Like the integrated cache in a single disk in a PC at that time, a certain amount of buffer memory is provided in the disk array to speed up interaction with the host. The cache interaction between the host and the disk array, and the interaction data between the cache and the specific disk. In applications, some common data needs to be read frequently. The disk array searches for frequently read data based on internal algorithms and stores the data in the cache, the speed for the host to read the data is accelerated. If the host does not read data from other caches, the array will directly read the data from the disk and transmit it to the host. For data written by the host, it is only written in the cache, and the host can immediately complete the write operation. Then, the cache writes data to the disk. Raid level

RAID levels include Raid0, Raid1, Raid2, Raid3, Raid4, Raid5, Raid6, Raid7, and Raid10.
Common levels in the production environment: Raid0, Raid1, Raid5, Raid10

Common Raid comparison

RAID level	Advantages	Disadvantages	Application scenarios
RAID0	Fastest read/write speed	No redundancy	High read/write requirements and Redundancy For example MYSQL Slave
RAID1	100% redundancy, Image	High read/write Performance	Independent, data is very important, Businesses that cannot crash
RAID5	Some redundancy exists, but only one disk can be broken, Good read performance,	Low Write Performance	General Business Use
RAID10	Fast read/write speed, 100% Redundancy	High Cost	High Performance and redundancy requirements Business, such as the master database Master node of the database and storage