sfs is a whole new file system, just like afs and pfs is.
i recomend sfs due to bad experience with pfs, but thats another story.
you need to reformat all of your hdd (or partisions which u want to have sfs on)
and remeber USE "QUICK FORMAT" and not full format as sfs and pfs use QF instead of normal slow formats.
remeber block size should be 1024 and not 512,
remeber to get the correct ID number and set as told in the doc the correct max transfer etc.
i advice you to read the doc instead of asking on here due to several reasons, 1 that is of big concern to many is...all old FFS tools wont work (disk salv , quaterbacktools etc) ..
the repair tools with sfs is few and not really tested (by me anyway) because i have so far been lucky and if it crash it has normally fixed it self on bootup ( auto repair )
anyway SFS is much faster than ffs and support 107 char long names.
check the sfs vs pfs threads here on amiga.org for more info.
goodluck!
