Dell PowerEdge T710 RAID Issues

Hi I have a Dell PowerEdge T710 with a PERC 6/i RAID controller. The Controller manages Five (5) One TB SAS drives spread between two RAID arrays (RAID 1 and RAID 5). About three weeks ago the Controller reported an issue (degraded) on the RAID 5 Array. I rebuilt the Array and within one week i got another degraded error but this time on the RAID 1 array (2nd drive). I have subsequently had to rebuild the same RAID Array (and hard drive) twice since then. I am trying to troubleshoot to determine whether the controller may be at fault or the hard drive. I suspect the latter but the fact that i had a problem on both arrays within a short time frame is also of concern. Your assistance would be appreciated!