Proposed Disk Array With 99.999% Availablity For 4 Years, Sans Maintenance
Found on Slashdot on Thursday, 29 January 2015
As the prices of magnetic storage continue to decrease, the cost of replacing failed disks becomes increasingly dominated by the cost of the service call itself. We propose to eliminate these calls by building disk arrays that contain enough spare disks to operate without any human intervention during their whole lifetime.
So basically they just stuff in tons of extra drives and hope that everything will work out. Not neccessarily an economic approach; and you might not even get that reliability if you picked Seagate Barracuda drives which have a failure rate of 43.1% in 2.2 years.