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There are three types of disk arrays, one is an external disk array cabinet, the other is an internal disk array card, and the third is software simulation.

External disk array cabinets are most commonly used on large servers with Hot Swap features, but these products are expensive.

Internal disk array cards, because they are inexpensive, require high installation technology and are suitable for technicians to use.

Using software emulation, it is not suitable for large data traffic servers because it will drag down the speed of the machine.

The disk array is directly connected to the host as a standalone system or connected to the host through a network. A disk array has multiple ports that can be connected by different hosts or different ports. A host connects to different ports of the array to increase the transfer speed.

As with the current single-disk internal integrated cache for PCs, there is a certain amount of buffer memory inside the disk array to speed up interaction with the host. The host interacts with the cache of the disk array, and the cache interacts with the specific disk.

In the application, some commonly used data needs to be read frequently. According to the internal algorithm, the disk array finds these frequently read data and stores it in the cache to speed up the reading of the data by the host. For other caches. The data that is not in the host is read by the host, and the array reads and transfers directly from the disk 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. Then the cache is slowly written to the disk.

Advantages of disk arrays:

Increase the transfer rate. RAID dramatically increases the data throughput (Throughput) of the storage system by simultaneously storing and reading data on multiple disks. In RAID, many disk drives can transfer data at the same time. These disk drives are logically a disk drive, so RAID can be used to achieve several times, dozens of times, or even hundreds of times the speed of a single disk drive. This is also the problem that RAID originally wanted to solve. Because the speed of the CPU grew rapidly, and the data transfer rate of the disk drive could not be greatly improved, there is a need to solve the contradiction between the two. RAID was finally successful.

Fault tolerance is provided through data verification. A normal disk drive cannot provide fault tolerance if it does not include a CRC (Cyclic Redundancy Check) code written on disk. RAID fault tolerance is built on the hardware fault tolerance of each disk drive, so it provides greater security. In many RAID modes, there are relatively complete mutual verification/recovery measures, even direct mirror backups, which greatly improves the fault tolerance of the RAID system and improves the system's stable redundancy.

Disk arrays can be implemented in two ways, namely "software array" and "hardware array".

The software array refers to the disk management function provided by the network operating system itself to configure multiple hard disks on the connected ordinary SCSI card into logical disks to form an array. Software arrays can provide data redundancy, but the performance of the disk subsystem will be reduced, and some reductions are still relatively large, up to about 30%.

What is a disk array? The hardware array is implemented using a dedicated disk array card. Hardware arrays provide online capacity expansion, dynamic modification of array levels, automatic data recovery, drive roaming, and caching. It provides solutions for performance, data protection, reliability, availability and manageability. The processing unit dedicated to the array card operates, and its performance is much higher than that of a conventional non-array hard disk, and it is safer and more stable.