3.4. Networking components

Of the four main hardware components, network I/O isn't likely to contribute to SQL Server performance bottlenecks. Tuning disk I/O, memory, and CPU resources is far more likely to yield bigger performance increases. That being said, there are a number of important network-related settings that we need to take into account, such as maximizing switch speed, building fault tolerance into network cards, and manually configuring network card settings.

3.4.1. Gigabit switches

Almost all servers purchased today come preinstalled with one or more gigabit network connections offering roughly 10 to 100 times the bandwidth of previous generations.

The speed of the network card is only as good as the switch port it's connected to. It's common for SQL Servers with gigabit network cards to be connected to 100Mbps switch ports. Gigabit switches should be used where possible, particularly at the server level between database and application servers.

In smaller networks, it's not uncommon for hubs to be used instead of switches. Hubs broadcast traffic to all network nodes. In contrast, switches intelligently route traffic as required, and should be used to reduce overall network traffic.

3.4.2. NIC teaming

To increase network bandwidth and provide fault tolerance at the network level, a technique known as NIC teaming can be used. NIC teaming involves two or more physical network interface cards (NICs) used as a single logical NIC. Both cards operate at the same time to increase bandwidth, and if one fails, the other continues operating. For further fault tolerance, each card is ideally connected to a separate switch. As we covered in chapter 2, NIC teaming is recommended for connections to an iSCSI SAN.

Although NIC teaming is a useful technique from both a performance and a fault tolerance perspective, there are some known limitations and restrictions regarding its use in a clustered environment, which we'll discuss in chapter 5.

3.4.3. Manually configuring NIC settings

Finally, most network cards offer an autosense mode that permits self-configuration to match its speed with the connected switch port speed. It's not uncommon for autosense to get it wrong, artificially limiting throughput, so NIC settings (speed and duplex) should be manually configured.

Chapter 6 provides a number of other best practices relating to network configuration, including protocol selection, port bindings, firewall configuration, and encryption.

Let's move from individual server components to the server as a whole, focusing on the trend toward server consolidation and virtualization.