This solution word for me  : in Terminal make a directory called ".fseventsd" (mkdir .fseventsd) in the drive mounted by time machine, and add a file inside called "no_log" (touch no_log).

It tells fseventsd process not to bother reading the backup drive.

The annoyance ceased immediately.

  Time machine backup worked flawlessly.

Solution found here : http://forums.macrumors.com/showthread.php?t=1103654

This solution worked for me:

In Terminal, make a directory called ".fseventsd" (mkdir .fseventsd) in the drive mounted by Time Machine, and add a file inside called "no_log" (touch no_log).

It tells fseventsd process not to bother reading the backup drive.

The annoyance ceased immediately. Time Machine backup worked flawlessly.

I found the solution on the MacRumors forums.