<i>&gt; You already have to use more disks for a RAID10 than in a RAID6, so I don&#x27;t see why this is that big of a deal.</i><p>Not really. RAID6 and RAID10 are only directly comparable at 4 disks as they have the same capacity with the same number of disks. And in that case RAID6 is strictly better than RAID10 (any 2 disks can fail vs at best 2 disks can fail).<p><i>&gt;But not more robust against failure, as I&#x27;ve already described (hopefully) rather clearly. If we want to play this game, I can keep adding more disks per mirror, and now my worst-case will match that of your n-parity array while having a vastly better best-case</i><p>This is simply not true. An n-parity array will always be strictly (and I mean strictly) more redundant than the equivalent RAID array. For 6 disks this means using 4 parity disks which allows failing any 4 disks which is RAID10&#x27;s best case but better than it&#x27;s worst case (any 2 disks can fail). If you go for 8 disks RAID10 allows a best case where 6 disks can fail which with a 6-parity raid is your normal case, and so on. Parity is strictly better than mirroring at redundancy its just usually not worth it for performance reasons. At the file level it may make sense though (Backblaze does file level 3-parity for example) as you can choose to take the hit only on certain files. Brtfs also allows per-file raid levels so it&#x27;s too bad they&#x27;re not pursuing that external patch for n-parity raid levels that the original article mentions.<p>(skipped some parts as the core of the issue is below)<p><i>&gt;And that&#x27;s fine, because if one of those manufacturers sold me a defective batch, the problem&#x27;s isolated to that side of the mirror. That&#x27;s my point; with RAID10, it&#x27;s no longer a game of sheer numbers of different models and manufacturers, but instead the more manageable strategy of giving each side of the mirror a different bathtub curve to ride, thus mitigating the chance of multiple hard drive batches failing at the same time.</i><p>This is not a RAID10 advantage it&#x27;s a way to mitigate the RAID10 disadvantage compared to parity. Parity RAID with the same capacity&#x2F;number of disks can survive more disk failures than RAID10 (as I explained above). In both cases you want the pool of N disks to be as diversified as possible to avoid correlation between failures. Parity exploits that lack of correlation completely (any disk failure is just like any other, it doesn&#x27;t matter which disk is which) whereas RAID10 will blow up earlier if all disks in one side fail at once so you mitigate that by making the two sides different.