&gt; RAID6 and RAID10 are only directly comparable at 4 disks<p>They&#x27;re really not <i>ever</i> directly comparable, because RAID10 isn&#x27;t a hard-and-fast RAID level like RAID6, but rather the combination of two (really, one plus a quasi-level, but whatever).  RAID10 encapulates any situation where mirrors are striped together.<p>&gt; 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).<p>You&#x27;re getting caught up on redundancy for a given total number of disks, and in the process missing the point entirely.  If we <i>really</i> want to play that game, then I&#x27;ll just roll a RAID1 (a.k.a. a RAID10 with only one set of mirrors) and call it a day, because with a n-disk array, a RAID1 will <i>always</i> be at least as redundant as the equivalent parity-based RAID (really, it&#x27;ll always be able to survive one more disk failure than an n-1 parity-block array; you can see this rather easily when comparing RAID5 with a three-way RAID1).<p>From there, my point should be more clear.  Just like how you can constantly add more and more parity blocks (and disks to handle them), I can constantly widen the mirror.  Eventually we&#x27;ll both get to the point where we realize &quot;what the hell are we doing; there&#x27;s 100 copies of every block; we should start adding some more non-redundancy disks&quot;, at which point RAID10&#x27;s advantages become more clear, since each mirror group added to the striped whole instantly bumps up capacity <i>and</i> the best-case without compromising the worst-case.  Meanwhile, you <i>do</i> have the advantage of having more flexibility in the quantity of disks added, but doing so doesn&#x27;t help your best-case unless you feel like resuming the whole &quot;let&#x27;s make every disk a parity or mirror disk&quot; arms race.<p>And before you mention it: yes, I know RAID1 isn&#x27;t <i>traditionally</i> counted under RAID10, but a RAID10 with only one mirror group is possible to configure using tools like `mdadm`, and while this wouldn&#x27;t <i>look</i> different from a RAID1 at first glance, it would certainly be different as soon as more mirror groups are added.<p>&gt; Parity is strictly better than mirroring at redundancy<p>I think this remark is the core of your misunderstanding here.  Are you really trying to claim than an n-sized parity array with n-1 parity blocks is <i>better</i> than a RAID1?  You might want to clarify your position there if that&#x27;s not what you meant to suggest :)<p>&gt; Parity exploits that lack of correlation completely (any disk failure is just like any other, it doesn&#x27;t matter which disk is which)<p>Which is exactly why you&#x27;re incorrect.  Since any disk failure is like any other, every single disk has to be unique in order for a parity-based array to benefit from any diversity.  With mirroring, you don&#x27;t have to go nearly as far for that same benefit; you just need <i>each mirror</i> to have a different bathtub curve.  That&#x27;s my point.<p>--<p>This has been a fun discussion, and there is certainly lots of room for debate on the merits of mirroring v. parity, but I&#x27;m starting to think that we should just agree to disagree on this one.