I created a file as root. then changed the ownership of the file to 'testacl' then changed the group to 'grpacl'. now when i tried to change the permissions for group using setfacl I'm getting the error saying operation not supported.

root@tortuga:/mnt/gluster# getfacl cleanup.sh 
# file: cleanup.sh
# owner: root
# group: root
user::rwx
group::r--
other::r--

root@tortuga:/mnt/gluster# chown testacl cleanup.sh 
root@tortuga:/mnt/gluster# chgrp grpacl cleanup.sh 
root@tortuga:/mnt/gluster# getfacl cleanup.sh 
# file: cleanup.sh
# owner: testacl
# group: grpacl
user::rwx
group::r--
other::r--

root@tortuga:/mnt/gluster# setfacl -m g:grpacl:rwx cleanup.sh 
setfacl: cleanup.sh: Operation not supported
root@tortuga:/mnt/gluster# 

But when I repeated the above exercise in back-end filesystem, I was able to to change that.

root@tortuga:/disk/samba-export# setfacl -m g:grpacl:rwx cleanup.sh 
root@tortuga:/disk/samba-export# getfacl cleanup.sh 
# file: cleanup.sh
# owner: testacl
# group: grpacl
user::rwx
group::r--
group:grpacl:rwx
mask::rwx
other::r--