Just a few notes to add to Doug's discussion
based on a few observations and some research at this end. The fact that the QNAP TS509 supports load balancing on it's dual LAN end had me thinking about Link Aggregation and 803.2ad. We also had several workstations with dual gigabit ports. So a few surprises:
1. The Dlink 1216T
"websmart" switch supports trunking, but does not explicitly indicate 803.2ad support. It does indicate support for Link Aggregation. So there looks to be a manual variant of 802.3ad which is referred to as such on some switches. This trunking setup on the 1216T does not work on the TS509 NAS although you can configure the trunk and set the NAS to its load balancing mode. So everything looks right, and you can connect but looking at the port stats..it's not load balancing. Qnap does indicate that the switch must support 802.3ad to work with the TS509 NAS load balancing option.
2. The Asus P5W-DH motherboards (older) have dual gigabit (Marvel Yukon) that don't advertise link aggregation. However you can go to Marvel's site and download their teaming driver tool..and it works. The software has you create a team, then add the two onboard NIC's to it. The driver allows you to choose Basic, Static, or Dynamic modes depending on your switch's capabilities. With the aforementioned 1216T the drive worked in static mode. The Marvell driver information indicates that the "Dynamic" setting will only work on switches with full 802.3ad support.
3. The Nvidia (680i) based Asus P5N32 (older) motherboard supports something they call teaming with is entirely managed at the workstation and did not work with a tunnel on the 1216T. Having the teaming mode enabled made no difference in our tests, but to be fair, we did not perform the multiple client load test. It this works, it would be a very cheap way to get link aggregation working, with even a very cheap switch.
In testing, the Marvel teamed NIC's on the P5W-DH motherboard did indeed work as advertised with multiple loads...the only Link Aggregation that we got working. The trunk was established on the 1216T switch and the driver on the workstation set to "Static" mode. Given the performance of this board with the onboard RAID chips, it would make a good base for an inexpensive server or NAS with some load balancing capabilities. We were able to hit the max tested transfer rates simultaneously to two test workstions (vs single tests) using this setup. In most cases hitting a single ethernet port device cuts it's output in half.
It would appear that the standard is a bit loose and that the terms "Trunking", "Teaming", and Link Aggregation" may represent some, but not necessarily all of the 802.3ad specification on a given device. I would guess that if the hardware does not specify 802.3ad, don't assume it has support for the full feature set of automatic link aggregration.
So the big question. Is there a 16 port gigabit switch out there with full
802.3ad support for under $800?