RAID (Redundant array of Inexpensive disks): Redundant array of independent hard disks, the basic idea is to combine multiple small hard disks together into a disk group to achieve performance improvement or capacity increase or redundancy through the management of software or hardware. Software RAID: The soft array provides the most basic raid fault tolerance through CPU IO operations and file settings on the hard disk. Hardware RAID: Hard arrays are IO-operated by independent hardware and rely less on CPU resources. Software RAID does not have much advantage over hardware RAID: Disadvantage: CPU occupancy HDD speed bus speed system reliability Advantage: No need to buy RAID card without considering the hard drive interface flexible to partition RAID level Linux so Ftware RAID Support levels 0, 1, 5, 6. RAID0: Emphasizes parallel access (that is, read and write performance is significantly enhanced), but does not have the capability to be redundant. If a disk fails, then no data can be recovered, and if a hard drive is taken from RAID0, RAID will not only lose one hard drive, but the entire RAID device would be filled with small voids. RAID1: True redundancy mode, but disk access performance is not as good as RAID0, at least two hard disks (the size must be equal), this mode will keep a hard disk image on the other hard disk. If the hard drive fails, all data remains intact, and if a spare disk is available, the hard disk image is rebuilt immediately. RAID5: With basic parity, the disk access performance ratio is very high, but it is difficult to predict, but also provides redundant mode, at least three hard drives above. If a hard disk fails, because of parity, the data can still be maintained, if there is a spare disk, the data will be rebuilt immediately, if the two hard disks fail at the same time, then all the data will be lost. In fact, a hard disk can also build RAID5, but requires more than three soft raid partitions, which is equivalent to three hard disks, so you can do RAID5.
RAID, soft raid, and hard raid
