NAND flash memory based Solid State Drive or Disk (SSD) have fundermantal barriers to widespread use in the enterprise. Especially, SLC flash costs 3-4 times more, making drivers too expensive for widespread use. So the solution to the cost problem is to use MLC flash, but this require overcoming the barriers of endurance, write performance, and reliability. To solve the problem, The venders of SSD have been appling the RAID technology in the SSD. There are two cases of product.
First, recovery and error detection method like RAID is applied for endurance in MLC flash because Error correction code (ECC) is weaker than HDD’s one.
Second, RAID’s performance is very good for I/O and endurance because of parallelism. I/O requests distribute among the disks in the RAID volume. RAID can reduce the latency. And RAID has parity bit . If a disk among the RAID Volume is failed, The parity bit and data bit in the other disk can be recovered the data in the failed disk.
