the author updated with this comment:
http://tech.oyster.com/how-to-build-a-40tb-file-server/?#com...
"Didn’t mean to give the impression that this is the only backup, it is not. It is the “warmest” one — first line. It does not share the same physical location with the primary storage box either, but is less than 2 miles away. So we can easily have a 2 hour recovery time without throwing away those astronomical monthly service fees. (Although many technologists will always prefer paying big bucks for the comfort of being cushioned from every angle by SLAs and such — nothing wrong with that, just a different approach.)
As far as TCO goes, it cannot get any lower since we already have one or two system guys handling all servers, as well as office workstations, etc.. This backup box takes up such a small fraction of their time that its almost negligible — several thousand annually at most. Same goes for power, etc — it is just one of many servers.
The disks are all Enterprise Class 2TB SATA-II, several different models. We were purchasing them right after the monsoon floods in Thailand constricted supply so our choices were somewhat limited as time was a factor.
Raid6 has come a long way since it’s early inception days, but is still a trade-off between raw storage capacity and processor utilization. HW RAID industry is now old enough to not have to wait for new products to mature as we used to when the technology itself was in its infancy. Old habits certainly die hard, but getting the “latest and greatest” was a conscious choice made for this specific problem, not submission to some immature fascination with “elite” new products, or however that may be.. This card has the best specs for Raid6 currently on the market — bottom line, period.
Big Kudos to all who made suggestions and participate in the discussion, keep it coming!"