SOLVED: What is NIC Teaming Doing & Does Link Aggregation Really Improve Performance?

When I started working NIC Teaming I thought that “link aggregating” two NIC’s would double my throughput and while that is possible, it is not likely and here is why.

When you link aggregate or Team Network cards using the common standards of the last decade, each NIC will still only connect to one system at its maximum speed (often 1GB).  Teaming / Link Aggregation lets that same server connect to a second system (say another server or a desktop PC) at it’s maximum speed (often 1GB).  So, if you have a single 10GB connection on SERVER A, and SERVER B has two 1GB teamed NIC’s, those two servers will only talk at a 1GB maximum.  The two 1GB NIC’s on SERVER B will not double the throughput to 2Gb.

This assumes you are using 802.3ad or 802.1ax “Link Aggregation Control Protocol” in a LAG (Link Aggregation Group).  If you are using a Team in a QoS (Quality of Service) mode, it will not provide any improvement in performance but will provide redundancy so if one link drops (i.e. cable gets unplugged), the other will pick up instantly.

This last third of this video explains the technicalities of Address Hashing and Hyper-V design which cause this “1 physical NIC per connection” situation:

There is a huge amount of documentation on this, but the above points are the most important to comprehend if you are new to Teaming.

OTHER READING:

 

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