不过RAID 6不同厂商的标准会有一些不同，Intel公司的P＋Q双校验RAID 6、NetApp公司的双异或RAID 6（也称RAID-DP）、X-Code编码RAID 6、ZZS编码RAID 6、Park编码RAID 6、EVENODD编码RAID 6等等。会不会是这些厂商自己RAID 6的限制呢？方便的话说一下这个说法的出处最好......
P+Q RAID 6：
XtremIO leads the market with up to 6 successive SSD failures per X-Brick and multiple simultaneous SSD failures across multiple X-Bricks (so long as each X-Brick is failing 1 SSD at a time). Out of >20,000 SSDs deployed, we have only had 6 SSD failures to date, so the odds of 2 simultaneous failures within the same X-Brick are astronomically small. Successive SSD failures are a much more likely failure event, especially with other AFA’s write hot spots (which XtremIO never has). The key question is what number of successive failures can competitive AFAs support? And for those concerned with the simultaneous failure risk within a single X-Brick, we are writing dual parity per X-Brick today and will productize the rebuild logic for simultaneous dual SSD failures in H1 (as a non-disruptive upgrade from 3.0). It is also worth noting that with spinning disks, you needed two parity drives not really for two drive failures, but for 1 drive failure, and a single sector error on any other remaining drive. On SSD’s, the drives themselves guard cells with correctable ECC and hence are not prone to a “bad sector”. Again, the real world risk of simultaneous SSD failure is remote- but the probability of successive drive failure in other AFAs is very high with hot spotting.