scan media folders on external hard drive

[zaragumma]

my media folder is on an external hard disk drive which is only plugged in when required. quite often i have to re-scan media folders before i can play the files, even though media library are showing those files. is there a way for the files in my media folder to be stored in subsonic permanently so i don't have to re-scan media folders before i can play the files? many thanks in advance.