Quote Originally Posted by hashbrowns View Post
This may seem like a dumb question, but while using MDADM, I'd like to make sure that I can mirror a current 160G sata drive to another 160G sata drive. Neither device is the boot filesystem. Both of them are currently formatted ext3. One has about 50G of stuff on it, the other is empty.

All I want to do is make a RAID1 array out of the two of them, but I don't want to bother copying this data somewhere else right now beforehand (unless I need to). So, if someone can confirm for me that the instructions listed on the first page (or here) for RAID1 will not damage the original data, that would be awesome. Thanks!
The instructions your linked to are for raidtools, so they would not go well with "while using mdadm" part of your request. I would locate mdadm specific instructions on how to accomplish what you want to accomplish.

You would be much better off backing up your data first before creating a raid, even if it's possible to create raid leaving 50GB of data in place (which I doubt, as mdadm needs to put a superblock somewhere on the drive which existing partition(s) will likely not allow to .. but I'm no expert here)