I agree on networking. Do 10Gbps over 1Gbps. A single drive copying from one machine to another can saturate the 1Gbps pretty easy. Conventional HD to HD copies, I can hit almost 2Gbps on large, zipped files.
posting basics but your probably want to read the VDEV layout whitepaper on different pool options. second link
BASICS
iX Systems pool layout whitepaper
Special VDEV (sVDEV) Planning, Sizing, and Considerations
