Shulou(Shulou.com)06/03 Report--

RAID disk matrix

Disk array: (Redundant Arrays of Independent Disks,RAID), which means "redundant array of independent disks".

Disk array: many cheaper disks are combined into a disk group with huge capacity, which uses the addition effect produced by individual disks to provide data to improve the performance of the entire disk system. Using this technology, the data is cut into many sections and stored on each hard disk.

Disk array: by using the concept of Parity Check, the data can still be read out when any disk in the disk matrix fails, and when the data is reconstructed, the data can be calculated and re-placed into the new hard disk.

Note:

In a very short time, the development of the disk is very fast, but although the capacity of the disk has expanded many times, it is difficult to improve the speed of data exchange between the disk and memory. In order to solve this problem, there is a "buffer memory", referred to as "cache".

How the disk matrix works: according to the internal algorithm, the disk array finds the frequently read data and stores it in the cache to speed up the host to read the data, while for the data that is not in the other cache, the host needs to read it, then the array reads the data directly from the disk and transmits it to the host. For the data written by the host, it is only written in the cache, and the host can complete the write operation immediately. It is then slowly written to disk by the cache.

Classification of disks:

1:RAID0: also known as disk mirroring. The relationship between disks is a replica. When writing to one disk, the mirrored ones of another disk are also written, which prevents the disk from being damaged and data lost, but this also reduces the utilization of the disk matrix. The highest utilization of disk mirroring is only 50%.

2:RAID1: striped storage. Writing data to each disk at the same time greatly improves the speed of data exchange between disk and memory. However, because the data written by each disk is not backed up, when a disk fails, it leads to data loss.

3:RAID0+1: somewhere in between.

Server cluster: server cluster refers to the centralization of many servers for the same service, which seems to the client that there is only one server. The cluster can use multiple computers for parallel computing to achieve high computing speed, and it can also use multiple computers for backup, so that any one machine can break down and the whole system can still run normally.

Note: the difference between server cluster and disk matrix:

These are two completely different levels of things. The server cluster improves the performance of the server, and the disk matrix improves the disk capacity and the speed of data exchange.

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