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How can VSAN network requirements affect performance?

Virtual SAN network configuration problems can detract from performance and availability. Update your drivers and check that no security products are blocking connections.

Continuous monitoring of VSAN network requirements is necessary to get the most performance and availability out of a virtual storage area network.

Network configuration problems can arise when a virtual SAN (VSAN) host system is unable to communicate with the network or exchange the intended traffic types. A status or summary report might indicate a network problem or misconfiguration. This is most likely the case when you deploy a VSAN platform as a cluster across multiple host systems and something disrupts communication between the hosts.

Clustered hosts improve throughput performance, which provides more systems to handle storage traffic. Clustered hosts can also improve VSAN resilience because other nodes will continue to function if one node fails.

When two or more members of a VSAN cluster can't communicate, the cluster can't function properly. The cause is usually a network configuration with unmet VSAN network requirements. There are four common network issues that can disrupt functionality.

Get the most bang for your buck with a VSAN

A common source of performance issues with VSAN is compatibility. Perform compatibility checks that capture the complex dependencies between the amalgam of hardware and software that make up a VSAN. Internal diagnostic tools can make this process easier.

Ensuring effective performance is important not only for the sake of the VSAN, but for the VMs that it might affect. Use performance metrics and alerts to spot VSAN issues before your VMs take a performance hit. I/O operations, memory use, processor use and network throughput can all cause problems.

A host might not have a driver installed. For example, VMware vSAN network requirements typically include a VMkernel adapter or driver on each host. If the driver is missing, the wrong version is present or the current version is damaged, the host might be unable to communicate with the network or other vSAN hosts.

Hosts must also be on the same network or network segment, so you might need to move one or more hosts within the network so all the hosts share the same subnet. This might require some physical connectivity changes to the network itself.

VSAN hosts will typically exchange metadata information using a group protocol, such as IP multicast. This means the network switch that connects all the cluster nodes must have multicast enabled. These VSAN network requirements might need a configuration change on the physical switch.

Finally, check that security products aren't disrupting the communication between cluster nodes. For example, a VSAN platform uses certain ports to exchange messages between cluster nodes. A firewall that blocks traffic on those ports will effectively block communication and prevent nodes from working together, so you should ensure that any firewalls allow traffic on the required ports.

This was last published in June 2018

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