I managed to set up a 4 drives Greyhole storage pool, system is up and running. Even managed to adopt an Ubuntu script so my N40L powers off if there are no active connections

What I am looking for now is a way to backup my data to an eSATA drive to be connected to my server.
IS there a how to on how I can have my Amahi detect and mount an eSATA drive on boot, IF it is available... and dont bother if it is not connected?
All advice seems to be focused on adding a permanently available drive, not temp backup drives.
THX!
BR Nico