CentOS - Oct 2014 - upgrade dhcpd failover set from centos 5.x ->7.x

Is there a less drastic way to upgrade a pair of dhcpd servers on
Centos 5.x than forklifting the old boxes out and hoping the
replacements work?.   The failover protocol seems to be incompatible
so I just upgrade one at a time....  Has anyone been through this with
a clever solution - like compiling a new dhcpd on the old boxes for an
easy rollback?

-- 
   Les Mikesell
      lesmikesell at gmail.com

I'm trying an installation of Centos-7 on a Lenovo RD340 E2420 with a 
raid 10 and a key for raid 5 controller
The installation stop at this line found on the debug
18:56:36,657 WARNING kernel:[111:138491] device mapper: ioct: error 
adding target to table

Is the any experience over this kind of problem

-- 
Michel Donais