Weird clicking problem

[elec999]

I have two western digital 500gb hard drive in raid1 on a pci silicon image 3114 controller. Its got two partitions one for windows one for my data, when I started to copy some data on my second partition, the hard drive started clicking, that would mean the drive is gone. When i reboot everything is fine, the raid controller doesn't see the array as damaged or anything, clicking is completety gone. Weird overall, the drives both pass the smart test.
Thanks