Optimize File Layout

The response time on my friend's iMac is getting slower. There are no obvious errors. I was thinking it may be as a result of the internal HDD layout.

My friend has a large music and photo collection which he regularly adds to and they are stored on the same partition as the Mountain Lion OS.

Some partition stats:

321GB Partiton size

109GB Free space

114GB iPhoto library

53GB iTunes library

I was wondering whether erasing the partition and restoring everything from the latest Time Machine backup would optimize the drive's layout.

I was also thinking this might be prudent to do before he upgrades to the Mavericks OS.