I have just bought two WD 3TB Reds (WD30EFRX) for a FreeNAS box and whilst doing burn-in testing it seems like one is consistently taking about 10% longer than the other. So far I've done: a dd read test of the whole device, a long SMART test and it's currently halfway through a badblocks -wvs. The second device is lagging behind the first on all of them. I'm running these commands on Debian stable in two Konsole tabs. Is there a reason this could be considered normal behaviour or is it worth running the tests independantly? They're both plugged in to the LSI 2308 (IT mode) on a Supermicro X10SL7-F.