I can't tell you from direct experience, as my only 're-buildable' array is a RAID1, but I'd assume it is the same - if the Intel Matrix Manager notices an array problem, it rebuilds 'on-the-fly' in the background without interrupting your work; mine is a systems engineering workstation with four OS's, two of 'em betas, and lots of flakey industrial logic design software, so I have more than my share of ugly crashes - (knock on formica) I've never had to resort to a backup! It does take a couple hours to completely rebuild a terabyte of RAID, though...