Let's pretend that you want to reliably backup 10 TB of data. How would you build such a system? Speed is somewhat important, but redundancy and reliability are the most important. I have been considering something along these lines: 2 x 5 drive, RAID5 arrays with 2TB WD Caviar Black drives in them. The first raid5 array will self-duplicate to the second raid5 array. That way, the raid5 array has redundancy in that if one drive fails, the array can self recover. And, if the entire first (or second) raid5 array fails, then you still have a copy of it. So this gives redundancy within the raid5 array itself, and it gives redundancy between the raid arrays. However, this does not protect against a catastrophic event because there is no offsite storage. Also, it does not protect against bit corruption (bit decay?) To actually do this on a Mac, I would use a Thunderbolt -> eSATA adapter, and I would use 2 5-drive RAID5 enclosures that have the raid controller and port multipliers built in. So the Mac would see two drives, and that would be that. An alternative way would be something like two thunderbolt pegasus raid5 setups, but that's pretty expensive. I believe it comes out to around twice the cost of my proposed setup, but it's really good hardware. Examples of proposed hardware: From OWC: http://eshop.macsales.com/shop/hard-drives/RAID/Rack_Mount/ From DatOptic: http://www.datoptic.com/hardware-raid-five-5-bay-1u-rackmount-esata-interface-rm5-r5.html And of course the LaCie Thunderbolt -> eSATA adapter. But.. If you were tasked to do this, how would you do it? How would you then solve the offsite backup and bit corruption problems? Things like Crashplan+ would take almost a year to backup to, and they only provide 1TB seed drives. Just curious for some input!