So, after giving it some thought... I can't use zfs (not enough ram, ZoL probably not the most favorable option) or btrfs (unstable, unrecoverable), there's no raid6 option for me. I guess I should just keep my mirrors separate? Then I can store all my longterm data to the second storage. I've been thinking this would probably overload it with occasional transfer bursts and mirror setup can mitigate that. But I'm really worried about the data corruption at this point. If I keep that second half separate and semi-offline, I could probably verify it with crc32 once in a while or something?

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The question still stands though, what should I tweak? This is my first 30TB storage.