Just was after finding out if anyone else has had this problem, if it is a problem!

My B7 A4 Tdi 170 has done 5k now and on one of the rear discs I have noticed the pads have not been making contact with a strip of the disc about an inch thick all way around the disc. ie it is always a different colour and feels slightly different.

Are the dealers likley to do anything with this? Is it a fault?