Gigabit
From LB Wiki
I'm often asked by those evaluating potential load balancer solutions for the SMB whether or not they should get Gigabit Ethernet, so I've put together this document to help make that determination.
When evaluating throughput needs in a web infrastructure setting, there are two primary concerns:
- Connectivity to the Internet
- Connectivity to the Servers
Connectivity to the Internet
In most cases, the only concern that you have with regards to the load balancers network speed is the speed of your network link to the Internet. If you've got a 10 Mbps link or even a T1 line (1.5 Mbps), then you don't have much of a need for Gigabit Ethernet. If you've got a Fast Ethernet connection and you're pushing 80 Mbps of traffic, then it probably won't be too long before you try to go over 100 Mbps, so Gigabit is a must.
The main benefit of Gigabit Ethernet is not so much that you can push 800 Mbps, it's that you can push 108 Mbps. It lifts the ceiling substantially, giving you room to grow when you're getting close to 100 Mbps.
Server Implications
In terms of Gigabit and servers implications, there are two primary architectures to consider. The first is a switch-based load balancer, where you plug your servers directly into the load balancer. The other is the appliance model, where you plug the load balancer and servers into a Layer 2 switch.
In the switch model, you're going to need Gigabit if you want your servers to communicate with each other. With the appliance model, you only need Gigabit Ethernet on your load balancer if you expect to push more than 100 Mbps to the Internet. The load balancer will not restrict or affect in any way connections that are not Internet-related.
In the diagram below, you see a fairly typical one-armed network configuration. The servers are connected to a Gigabit switch via a Gigabit link, while the network uplink and the load balancer are connected with 10 Megabit and 100 Megabit links, respectively.
Diagram 1: One-armed Network
In this configuration, communications between the servers can happen at Gigabit speeds. Since everything is on the same subnet, the load balancers and/or default gateways are not involved. Granted, he maximum speed the Internet can communicate with these servers is 100 Mbps, and that's cut down to 10 Mbps by the uplink to the network provider (which is fairly typical).
Vendors and Gigabit
Of course today Gigabit Ethernet is prevalent, and most load balancers include Gigabit. The choice is more often a part of the decision process for the value market load balancers. The sub $5,000 USD load balancers are often equipped with 10/100 Fast Ethernet instead of Gigabit.
10 Gigabit Ethernet
The same theory is true for 10 Gigabit Ethernet. The reason to look at 10 Gigabit is not to push 8 Gigabits, but to push 1.08 Gigabits to the Internet. If you're not pushing that, or even close, even having 10 Gigabit on your infrastructure side will not require your load balancer to be 10 Gigabit.
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