In addition to running the jenkins instance, the build master serves git, dhcp, salt, and buildresults to the test pool. We chose a system with the following characteristics:
lots of ram: Parsing junit xml for will exhaust memory. a single result file can be >2GB.
multiple nics: Test systems sit on an isolated subnet and access eachother via mdns. One nic on the master bridges the system to the external network. Other nics are teamed to increase nfs/rsync throughput to test systems on the subnet.
multiple drives: All devices other than the boot volume are configured in raid0 for throughput.