With the answer being "two" ... one on the front, and one on the back.
However, that's not entirely true. There was a band years ago that came out with a record that had two intertwined grooves on each side. Meaning you could put the needle down in two places (randomly) and half the time you'd hear a different record (half the length of a standard lp of course). The record itself was not monumental, and the band I think lost money due to the higher cost of this unusual production.
Although applied to the philsophy of mind, it made me wonder if the same thing is not possible with a brain.
The level of redundancy is probably greater than two fold, since people have lost half their brain at birth and still adapted to function normally.
This means there could be (in theory) two complete, fully functioning brains superimposed in the same head. That never interacted with each other. The brain that was hooked up the the sensory equipment and muscles would never even know the other person existed.
Just an odd thought

:driving: