Anyway I was experimenting more and discovered something against docs. These time I created newfs on pendrive so if fs get corrupted it will not break nothing. It will be dd-zeroed and formatted anyway.
Manual of mount says: The options async and softdep are mutually exclusive. But I have discovered a way to change state and mount prints that fs is asynchronous and softdep at the same time. # newfs -t ffs /dev/rsd2a # mkdir /mnt/pendrive_ffs # disklabel sd2 | grep duid duid: 5d0d4f4f380893e0 # mount -o softdep 5d0d4f4f380893e0.a /mnt/pendrive_ffs # mount | grep pendrive_ffs /dev/sd2a on /mnt/pendrive_ffs type ffs (local, softdep) mount -u -o async 5d0d4f4f380893e0.a /mnt/pendrive_ffs # mount | grep pendrive_ffs /dev/sd2a on /mnt/pendrive_ffs type ffs (asynchronous, local, softdep) # mount -u -o nosoftdep 5d0d4f4f380893e0.a /mnt/pendrive_ffs # mount | grep pendrive_ffs /dev/sd2a on /mnt/pendrive_ffs type ffs (local, softdep)
