Yes, but no. If the chance of each drive failing is 1 in 100, their chance of failure is the same, but the chance of both failing would be 1 in 10000 (1/100 * 1/100) (assuming their failures are independent of each other, i.e. they weren't ruined by some other effect (power surges, murphy's law, etc.) which coincidentally affected them both at the same time. rather than image the drives and see how long they run, why not put them in a pc and run a test that gives more definitive results (mfr. diagnostic, spinrite, etc). If the drives are going bad, just about any utility that can read the hdd SMART info will tell you more than just imaging and trying again.