Just a final thought….
Ever contemplated about a tiny storage ceph-cluster, each disk connected to an R-pi?
No spofs, and easier to maintain and upgrade…
RAID boxes have some useful capabilities like staging power to drives on startup.
There are use cases that do trivial computations on 1000's of files where it would
be really nice to have lots of cheap compute nodes, each with a disk, so you could
distribute the files to the disks and have the output files appear in some network
filesystem.
There are some youtube videos for R-pi NAS -- getting power to all the drives is
an issue and without staging you need a very capable PS.