division management

I am a manager for a division that support and administer a hundreds of servers and 3 mainframe spread out over 3 Datacenters located in 3 different cities.
I am hesitant on how I can divide the division into a groups or teams of business units.
I reached to two solution as follows:
solution A:
         To divide into 3 teams or groups, one team for each datacenter.
Solution B:
         To divide into functional groups. means servers admin group, mainframe group,   Database group, and backup group.
in this solution, the group leaders will be a far away from their members.