"Hitless-failover Enable": Can Not Configure On The FCX648S Brocade Switch

I was configuring a stack on a couple of Brocade switches that I was setting up for a SAN environment.  I couldn't figure out why I couldn't run the 'hitless-failover enable' command.  As it turns out, the revision of code that came on the Brocades would not support that command.  I did some research and found that revision 7.2.00 is where the command starts in the Brocade IOS.  So, if you need this command like I did, you will need to upgrade your firmware to at least 7.2.00.