Consider networking features that can provide availability, security, and bandwidth guarantee in a vSAN cluster.
For details about the vSAN network configuration, see the vSAN Network Design Guide.
Networking Failover and Load Balancing
vSAN uses the teaming and failover policy that is configured on the backing virtual switch for network redundancy only. vSAN does not use NIC teaming for load balancing.
If you plan to configure a NIC team for availability, consider these failover configurations.
|Teaming Algorithm||Failover Configuration of the Adapters in the Team|
|Route based on originating virtual port||Active/Passive|
|Route based on IP hash||Active/Active with static EtherChannel for the standard switch and LACP port channel for the distributed switch|
|Route based on physical network adapter load||Active/Active|
vSAN supports IP-hash load balancing, but cannot guarantee improvement in performance for all configurations. You can benefit from IP hash when vSAN is among its many consumers. In this case, IP hash performs load balancing. If vSAN is the only consumer, you might observe no improvement. This behavior specifically applies to 1-GbE environments. For example, if you use four 1-GbE physical adapters with IP hash for vSAN, you might not be able to use more than 1 Gbps. This behavior also applies to all NIC teaming policies that VMware supports.
vSAN does not support multiple VMkernel adapters on the same subnet. You can use different VMkernel adapters on different subnets, such as another VLAN or separate physical fabric. Providing availability by using several VMkernel adapters has configuration costs that involve vSphere and the network infrastructure. You can increase network availability by teaming physical network adapters.
Using Unicast in vSAN Network
In vSAN 6.6 and later releases, multicast is not required on the physical switches that support the vSAN cluster. You can design a simple unicast network for vSAN. Earlier releases of vSAN rely on multicast to enable heartbeat and to exchange metadata between hosts in the cluster. If some hosts in your vSAN cluster are running earlier versions of software, a multicast network is still required. For more information about using multicast in a vSAN cluster, refer to an earlier version of Administering VMware vSAN.
vSAN 7.0 Update 2 and later releases can use Remote Direct Memory Access (RDMA). RDMA typically has lower CPU utilization and less I/O latency. If your hosts support the RoCE v2 protocol, you can enable RDMA through the vSAN network service in vSphere Client.
- Each vSAN host must have a vSAN certified RDMA-capable NIC, as listed in the vSAN section of the VMware Compatibility Guide. Use only the same model network adapters from the same vendor on each end of the connection. Configure the DCBx mode to IEEE.
- All hosts must support RDMA. If any host loses RDMA support, the entire vSAN cluster switches to TCP.
- The network must be lossless. Configure network switches to use Data Center Bridging with Priority Flow Control. Configure a lossless traffic class for vSAN traffic marked at priority level 3.
- vSAN with RDMA does not support LACP or IP-hash-based NIC teaming. vSAN with RDMA does support NIC failover.
- All hosts must be on the same subnet. vSAN with RDMA supports up to 32 hosts.
Allocating Bandwidth for vSAN by Using Network I/O Control
vSAN traffic can share 10-GbE physical network adapters with other system traffic types, such as vSphere vMotion traffic, vSphere HA traffic, and virtual machine traffic. To guarantee the amount of bandwidth required for vSAN, use vSphere Network I/O Control in the vSphere Distributed Switch.
In vSphere Network I/O Control, you can configure reservation and shares for the vSAN outgoing traffic.
- Set a reservation so that Network I/O Control guarantees that minimum bandwidth is available on the physical adapter for vSAN.
- Set shares so that when the physical adapter assigned for vSAN becomes saturated, certain bandwidth is available to vSAN and to prevent vSAN from consuming the entire capacity of the physical adapter during rebuild and synchronization operations. For example, the physical adapter might become saturated when another physical adapter in the team fails and all traffic in the port group is transferred to the other adapters in the team.
For example, on a 10-GbE physical adapter that handles traffic for vSAN, vSphere vMotion, and virtual machines, you can configure certain bandwidth and shares.
|Traffic Type||Reservation, Gbps||Shares|
If the 10-GbE adapter becomes saturated, Network I/O Control allocates 5 Gbps to vSAN on the physical adapter.
For information about using vSphere Network I/O Control to configure bandwidth allocation for vSAN traffic, see the vSphere Networking documentation.
Marking vSAN Traffic
Priority tagging is a mechanism to indicate to the connected network devices that vSAN traffic has high Quality of Service (QoS) demands. You can assign vSAN traffic to a certain class and mark the traffic accordingly with a Class of Service (CoS) value from 0 (low priority) to 7 (high priority). Use the traffic filtering and marking policy of vSphere Distributed Switch to configure priority levels.
Segmenting vSAN Traffic in a VLAN
Consider isolating vSAN traffic in a VLAN for enhanced security and performance, especially if you share the capacity of the backing physical adapter among several traffic types.
If you plan to use jumbo frames with vSAN to improve CPU performance, verify that jumbo frames are enabled on all network devices and hosts in the cluster.
By default, the TCP segmentation offload (TSO) and large receive offload (LRO) features are enabled on ESXi. Consider whether using jumbo frames improves the performance enough to justify the cost of enabling them on all nodes on the network.