To    configure journaling on    the UFS    file system using 
gjournal, one    should
     first create a 
gjournal provider using the    
gjournal utility, then run
     
newfs(8) or 
tunefs(8) on it with the 
-J flag which    instructs UFS to coop-
     erate with    the 
gjournal provider below.  There are    important differences
     in    how journaled UFS works.  The most important one is that 
sync(2) and
     
fsync(2) system calls do not work as expected anymore.  To    ensure that
     data is stored on the data    provider, the 
gjournal sync command should be
     used after    calling    
sync(2).  For the best performance possible, soft-
     updates should be disabled    when 
gjournal is used.    It is also safe    and
     recommended to use    the 
async mount(8) option.