Synthetic ACLs become real ACLs when any permission activity happens in a Windows context.  Even something as simple as removing everyone from a Synthetic ACL would trigger this.  As long as you only work with the POSIX bits, it will stay synthetic.  If you need to back out and go to back to Synthetic ACLs you can use chmod -b on the cluster and it will "blow away" the ACL.
Community,   How important is it that /ifs retains its synthetic ACL stamp?  Below is a directory I created and altered the permissions and the synthetic ACL stamp disappeared.  I need to know if there is a way I can alter the directory/file permission without disturbing the synthetic ACL setting?  That is if there is some importance in keeping it.  Isilon-2# ls -lzed root_test drwxr-xr-x    2 root  wheel  0 Apr 20 12:58 root_test  OWNER: user:root  GROUP: group:wheel  SYNTHETIC ACL  0: user:root allow dir_gen_read,dir_gen_write,dir_gen_execute,std_write_dac,delete_child  1: group:wheel allow dir_gen_read,dir_gen_execute  2: everyone allow dir_gen_read,dir_gen_execute  Isilon-2# chmod +a group everyone allow dir_gen_write,delete_child /ifs/data/root_test  Isilon-2# ls -lzed root_test drwxrwxrwx +  2 root  wheel  0 Apr 20 12:58 root_test  OWNER: user:root  GROUP: group:wheel  0: user:root allow dir_gen_read,dir_gen_write,dir_gen_execute,std_write_dac,delete_child  1: group:wheel allow dir_gen_read,dir_gen_execute  2: everyone allow dir_gen_read,dir_gen_write,dir_gen_execute,delete_child  I know if you make changes to the permissions using the Filesystem explorer page in the WebUI the synthetic ACL stamp is retained, but is there a way to retain it via CLi?    Thank you,
Isilon - /ifs and synthetic ACL