Sounds like you are unlucky anyway ... could be the drives are failing, could be the backplane/cable or controller, or it could be firmware related. What I would do is reseat the RAID controller, the drives, and the cables that run from the controller to the backplane (both ends).  Then, run 32-bit diagnostics (bootable - from support.dell.com) on the drives - not the quick tests, but the full diagnostics.  Get rid of any drives that fail; the ones that pass, keep.  Update the BIOS, ESM/BMC, RAID, HDD firmwares.  Then, try again.
I know "anythign is possible", but I can't believe what happened with my aging ( 4 years old) PowerEdge 2900 with Perc 6i .  The machine had 8 300GB drives in a Raid-5 configuration.  One Wedneday morning, post Micrososft Update Tuesday, it reported a failure with one of the drives, so my Raid-5 was degraded.  I called Dell, but there basically aren't any replacement drives available due to the Thailand flooding and I don't have any spares either.  So I offload all the data on the machine and make the decision to rebuilding the entire machine as a Raid-6 with 7 disks, and then reload the data. But after recreating the Virtual disk and starting to initialize, 2 more drives report in a failed?  How can this be?  I rebooted the machine and tried to force online the failed drives, recreated the VD,  but nothing seems to work. Suggestions or did I just get "lucky?    
Multiple drive failures in one day?