What is the point to run RAID6 on 4 drives, instead of RAID10? With both, half the space is usable, but with RAID10 read speed is twice as high, and resilvering is twice as fast.
RAID6 makes sense for 5-8 drives.
RAID6 makes sense for 5-8 drives.
With RAID10, if the 'wrong' two disks fail, the array will go offline.
With RAID6, any two disks can fail and the array will still be online.
EDIT: The author has also demonstrated that they've gone through various growth permutations over the years. 4 disk RAID6 under md-raid has a supported growth mechanism, allowing you to add additional disks and have it restripe data automagically for you. It's not a good idea as far as performance is concerned, but for a home use nas that is primarily intended for streaming media, it's not a major issue, and enables you to grow to your heart's content (even if it is a bad idea, as I successfully proved growing from 4 disks to 16 over a few years, before respinning as multiple 6-disk arrays)
The testing is focused on ZFS but, quoting from the conclusion: If you're looking for raw, unbridled performance it's hard to argue against a properly-tuned pool of ZFS mirrors. RAID10 is the fastest per-disk conventional RAID topology in all metrics, and ZFS mirrors beat it resoundingly—sometimes by an order of magnitude—in every category tested, with the sole exception of 4KiB uncached reads.
[0] https://arstechnica.com/gadgets/2020/05/zfs-versus-raid-eigh...
Emphasis on 'properly-tuned'. This doesn't hold as true as the OP states for the defaults (which is what the majority of home users will be using)