How to defrag XFS file-system if xfs_fsr exits with "no improvement will be made"?

I am trying to defrag a heavily fragmented XFS file-system on a CentOS 6.6 machine:

[root@server opt]# xfs_db -c frag -r /dev/md3
actual 598, ideal 215, fragmentation factor 64.05%

However, when I attempt to launch the xfs_fsr utility, it exits with the message No improvement will be made (skipping):

[root@server opt]# xfs_fsr -t 25200 /dev/md3 -v
/opt start inode=0
ino=536871105
No improvement will be made (skipping): ino=536871105

How can I get this to defrag?