I have several 5 - 10 websites that use adsense. I am trying to figure out the best way to set up my adsense channels.

Currently the system I am think in about is:

Site Name + Unit Type + Placement on Page

I can not figure out from this system how determine exactly how a specific unit is doing. Maybe I need a system like this:

Site Name + Unit Type + Placement on Page + Unique identifier


Is there another solution I am overlooking?

How does everyone manage their channels?