Strange external hard drive clicking after disk encryption

Hi folks,

I have a late 2011 Macbook Pro with OS X 10.8.4 Mountain Lion and have used this 2TB external USB 2.0 drive (enclosure with a Western Digital Black 2TB) since I bought the laptop without any issues. Just enabled encryption for the disk and after a day of encrypting, I verified with "diskutil cs list" that the drive was done, and the HDD indicator on the drive stopped.

However, now, even when there is no external disk activity, the hard drive has consistent clicking (about 3-4 clicks per second) and the HDD light is not on. Accessing the drive is normal with normal hard drive sounds. In the past, when I unmounted the volume I could hear the drive spin down, but now, it appears to unmount normally but the drive does not spin down and the clicking continues. If I power off the drive, it sounds like I am forcing it to spin down now.

It seems like there's a low level process doing something with my data. Has anyone else encountered this?

Thanks a ton!

 

Interesting... Well I also posted the same question on Apple Discussions and everyone suspected a failing drive... My drive continued to click even after decrypting, so I replaced it..