RAID (Redundant Disk Array) is a technology used to improve storage performance and reliability by combining multiple disks together to create a larger storage volume. There are several different levels in RAID technology, each with its own data protection and performance characteristics. However, RAID technology is not perfect, and the three levels of RAID2, RAID3 and RAID4 are gradually being eliminated in practical applications. So, why are these three RAID technologies being eliminated?
First, let's look at RAID2 technology. RAID2 uses Hamming code to provide data protection, storing only a subset of data bits on each disk. Although Hamming Code can provide a high level of data protection, it requires computing and storing a large amount of check information, so the performance of RAID2 is relatively low and requires at least 9 hard drives to achieve. In addition, for modern storage systems, the data protection capabilities of RAID2 can no longer meet current needs, so RAID2 technology has been eliminated.
Next, let's look at RAID3 technology. RAID3 uses parity to provide data protection, with equal block sizes on all disks. RAID3 requires at least 3 hard disks and requires a dedicated parity disk to store parity information. However, since each block of data needs to be computed and stored on parity disks, the performance of RAID3 is also low in practical applications and inferior to other RAID levels. In addition, RAID 3 cannot handle multiple hard drive failures, so its reliability is also challenged. As a result, RAID3 technology has also been phased out.
Finally, let's look at RAID4 technology. Unlike RAID3, which divides data into equal-sized chunks, parity information is stored on separate parity disks. RAID 4 requires at least 3 hard drives, but its performance is relatively low because all data access needs to go through parity disks. Also, if the parity disk fails, the entire RAID system will not work. In contrast, RAID5 technology uses distributed parity to provide a higher level of data protection and reliability, and allows multiple hard drives to read and write simultaneously, making it more efficient and practical. As a result, RAID 4 technology is also being phased out.
In summary, in the development of RAID technology, the three levels of RAID2, RAID3 and RAID4 have been gradually eliminated mainly because their performance and reliability cannot meet the needs of modern storage systems. As storage technology continues to evolve, so does RAID technology, and new RAID levels such as RAID6, RAID10, RAID50, and RAID60 provide higher levels of data protection and performance and are better suited to the needs of modern storage systems. Therefore, in order to ensure the stability and performance of the storage system, we need to choose the RAID level that best suits the current needs and avoid using outdated RAID technology.