Thanks, costs may have strayed me from going that wide. But at the same time I get to start with a solid vdev capacity to get me started.

My earlier research tells me 6-8 are the optimal widths for a raidz2, and I certainly want capacity over performance so I guess it makes sense to bite into the costs up front to gain that ~16TB in storage.

... Having healthy concerns involving parity is inherently not bad to investigate if you know about the weaknesses around e.g. the Galois algebra and Reed Solomon code for typical RAID6 parity calculation. Such as having a corruption at the same byte positions on 2 drives can actually introduce corruption instead of fixing it. Not likely, but an example of a possibility merely introduced by increased complexity. But I'll accept that ZFS perhaps has internal mechanics that may mute it and I'll lay them to rest... I got enough on my mind.

Not only media, got a few thousand small backup files as well. So I'll just stick with my default choice of 4K/ashift=12.