Tracker is turned on in Ubuntu by default. I personally turn it off because it uses up system resources that I don't want to spare and I don't keep a lot of data on my Mini. Other users have concerns with Tracker's wear and tear on their system drives. The Mini 9 ships with a solid-state hard drive that has a finite number of erase/write cycles that the flash memory can tolerate. There are also users who disable Tracker because they feel it is not a very good indexing program.
While I don't need an indexing program on my Mini, I have been testing Tracker on my desktop. I find that it works well.
But whatever your reason, disabling Tracker is easy.
To Stop Tracker From Loading on Start Up:
Under System>Preferences>Sessions
Uncheck both Tracker and Tracker Applet
To Disable Indexing:
Under System>Preferences>Search and Indexing
Uncheck both enable indexing and enable watching
Changes will take effect next time you restart your PC.
Remove Tracker
If you prefer you can chose to remove Tracker from your system:
In a terminal type
sudo apt-get remove tracker tracker-search-tool tracker-utils
For more information about solid-state hard drives.