Dual booting; just a small problem.

I am not sure the appropriate place to post this so feel free to tell me a better subreddit. Thank you!

I'm having a problem with dual booting using multiple hard drives My main hard drive has OS X Lion installed and the second one is running Arch Linux and it is formatted to ext4.
Whenever I boot into OS X, I get an error that says "the disk you inserted was not readable by this computer", which seems to make sense to me because Lion can't read ext4.
The problem is that this error pops up every time I turn the computer on. I want to get rid of it and stop it from popping up.

Any ideas how?