Drive access lights normally on when idle?

[Craigcv]

We have just installed a second 4314 drive array enclosure hooked to  an ML330 server. Both arrays are raid 5 and array one has been functioning well for years.  Array 2 has 6 x 10K 300meg drives as a seperate logical drive, all looks good.  However, it appears that with array 2 the hard drive activity lights are constantly on when idle and flash when being accesssed.  The original array one seems to have the drive access lights normally off and flashing when accessed, although I can't tell for sure as array one is being accessed quite constantly.  Question: Is it normal for the HD access lights to be on when the drives are actually sitting idle? Thanks in advance for your help.