Redundant Arrays of Independent Disks, also known as RAID, refers to an array of independent disks with redundancy capabilities.
A disk array is a combination of many cheaper disks that form a large capacity disk group, utilizing the additive effect of individual disks providing data to improve the overall performance of the disk system. By utilizing this technology, data can be divided into many segments and stored separately on various hard drives. The disk array, as an independent system, is directly connected outside the host or connected to the host through a network. The disk array has multiple ports that can be connected to different hosts or ports. Connecting a host to different ports of the array can improve transmission speed.
The styles of disk arrays can be divided into three types:
1. External disk array cabinet. External disk array cabinets are most commonly used on large servers and have the characteristic of being hot swappable, and these products are very expensive;
2. Internal disk array card. Internal disk array card, relatively inexpensive, but requires advanced installation technology, suitable for technical personnel to use and operate;
3. Use software to simulate. The use of software simulation refers to the configuration of multiple hard drives on a connected ordinary SCSI card into logical disks through the disk management function provided by the network operating system itself, forming an array.
Advantages of RAID:
1. Increase transmission rate;
2. Provide fault tolerance through data validation.
Disadvantages of RAID 0 and RAID I:
1. RAID 0 has no redundancy function. If a disk (physical) is damaged, all data cannot be used;
2. The maximum utilization rate of RAID 1 disks can only reach 50% (in the case of using two disks), which is the lowest among all RAID levels;
3. RAID 0+1 can provide data security for the system, but the degree of protection is lower than Mirror and the disk space utilization is higher than Mirror.
