If you have a number of files which start with the name “build_hd_index” located within the /tmp directory on your system, then it is possible that you have enabled ARD (Apple Remote Desktop; AKA Remote Management) on your system and this is performing various indexes of the storage devices on your system.
It should be possible to disable this indexing from a Remote Desktop (Administrator) system.
Quoted from Apple : “Adjust the Data Collection settings on each admin system.”
Finally, you may wish to consider disabling ARD on your backup server.