iPhoto library AND time machine backup on my book Live Duo?

I’m setting up a new MacBook Air which is replacing a much older MacBook which had significantly more onboard storage. My wife will also use this new machine when her laptop goes the same way. To get around the storage issue I got this 4TB network drive.

I’m in the process of transferring my iTunes files across to the MBLD, building up a new library as I go in the preset music partition

The time Machine backup appears to be working.

The iPhoto online help says that problems will ensue if you place your iPhoto library on the same device as your time machine backup because the file permissions will be in conflict. Is this true when using the preconfigured partitions on the MBLD? If not then I will go ahead and copy my photo library into the photos partition. If it is true then I’m probably looking at attaching yet another HD to the network to hold photos (so that they can be saved in one place and shared locally).

Many thanks