I do RAID data recovery for a living. Customers always think that '2 drives failed at the same time'. Thats not what usually happens. What really happens is that 1 drive fails and the raid does what it supposed to do - it keeps on functioning. Sometimes for months. Then the second drive fails and it stops. They call in the IT guys and it appears that '2 drives failed at the same time'. Not.. Most raid data loss is caused by IT guys trying to fix it - because its a raid and its redundant and it cant be hurt so let me start swapping stuff and rebuilding and destroying...