[CentOS-virt] "CentOS on a stick"

Hi, I'm looking into setting up a redundant firewall and I'm wondering how feasible it is to use an USB stick as the only storage device in these systems (i.e. no HDs). The logs will go to a remote logging server but I'm wondering what else needs to be changed to make something like this possible.

The idea is to have both systems running independent of each other with the iptables rules being manually kept in sync and conntrackd syncing the connection tracking data.

Has anyone experience with this and how would one go about creating such a USB drive? So far I've only used USB for installation but not as an actual root fs itself.

Regards, Dennis