[CentOS] 12-15 TB RAID storage recommendations

>I would like to build a 12-15 TB RAID 5 data server to run under
>ContOS. Any recommendations as far as hardware, configuration, etc?

This comes up often:)
Things to keep in mind when using large discs if you suffer a failure,
while rebuilding in a degraded state it's not impossible or unlikely to
drop another disc loosing it all.

Rebuild times especially on busy arrays with large discs take lots of
time...