A lot of servers do raid. disk array is a combination of multiple disks that are combined into a single disk group with different functions by means of a special array card. Nowadays, many large server vendors are using disk array function on their cloud hosts in general, which can better protect the security of data.

RAID is a redundant array of multiple hard disks. Although RAID contains multiple hard disks, it appears as a separate large storage device under the operating system. There are three main uses for RAID technology in storage systems:

1. Providing disk spanning by organizing multiple disks together as a logical volume;

2. Increasing the speed of accessing disks by dividing data into blocks and writing/reading to/from disks in parallel;

3. Providing fault tolerance through mirroring or checksumming operations. Provides fault tolerance.

Originally, RAID was developed primarily for cost savings, at a time when the combined price of several small-capacity hard disks was less than that of a large-capacity hard disk. RAID's role in cost savings is not obvious at this point, but RAID can take full advantage of multiple hard disks.

Achieving speeds and throughputs that far exceed those of any individual hard disk. In addition to performance improvements, RAID provides good fault tolerance, allowing you to continue working in the event of a problem with any of the hard disks, without being affected by a damaged drive.

RAID technology is categorized into several different levels, each offering different levels of speed, security, and cost-effectiveness. Choosing the appropriate RAID level for the situation will meet the user's requirements for storage system availability, performance and capacity.

Extended information:

Commonly used RAID levels are the following: NRAID, JBOD, RAID0, JBOD, and RAID3. JBOD, RAID0, RAID1, RAID0+1, RAID3, RAID5 and so on. Currently, RAID5 and RAID (0+1) are often used.

RAID0 favors efficiency, with 100% disk utilization.

RAID1 is on the safe side, with only 50% disk utilization.

RAID0 is the combination of multiple (at least 2) hard disks into one logical disk, the data read and write to each hard disk at the same time, different hard disks to write different data, fast.

raid1 is to read and write to two hard disks at the same time (the same data). Emphasizes data security. It is more wasteful.

raid5 is also a combination of multiple (at least 3) hard disk into a logical disk to use, the data will be read and written to establish parity information, and parity information and the corresponding data are stored on different disks. When data corruption occurs on one of the RAID5 disks, the remaining data and the corresponding parity information will be used to recover the corrupted data. It is equivalent to a combination of raid0 and raid1.

raid10 is raid1+raid0, which is more suitable for high speed requirements, and to be completely fault tolerant, of course, ￥ also a lot of time. A minimum of 4 hard disks are required (note: when doing raid10, you need to do RAID1 first, and then make several RAID1s into RAID0s, so that you have higher reliability than if you do RAID0 first, and then RAID1)

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