7.3 Network Considerations
The network is a critical component that is required for cluster node communication locally and across sites. In addition to normal network communications, Microsoft SQL Server in a non-shared disk, high availability solution, such as AlwaysOn Availability Groups, also utilizes the network for data replication between replicas. Especially in synchronous replication mode, the performance of the solution is highly dependent on the network bandwidth and latency.
Consider the following network configuration guidelines to achieve a robust technical platform and optimal performance:
• Configure appropriate network adapters on the host and virtual machines to separate networks used for different vSphere, virtual machine, and application purposes. For instance, you might want a separate network for data replication, heartbeat, vSphere vMotion, management VMkernel, and so forth.
• If using iSCSI at either the host level or in-guest, the network adapters must be dedicated.
• Use the VMXNET3 paravirtualized NIC with all Windows Server 2012 R2 instances. The VMXNET3 is optimized for virtual environments and is designed to provide best performance.
• Enable jumbo frames for the iSCSI and vSphere vMotion network.
• Always employ static IP addresses for network interfaces in a Microsoft Windows server cluster. Using a dynamic configuration through DHCP is not recommended, because the failure to renew a DHCP lease could disrupt cluster operations.
• If deploying AlwaysOn Availability Groups in synchronous commit mode, use a high-speed network for replication traffic. Confirm that the bandwidth and latency of the network is sufficient to support the amount of Microsoft SQL Server transaction traffic.