Migration with vMotion requires correctly configured network interfaces on source and target hosts.

Configure each host with at least one network interface for vMotion traffic. To ensure secure data transfer, the vMotion network must be a secure network, accessible only to trusted parties. Additional bandwidth significantly improves vMotion performance. Consider that when you migrate a virtual machine with vMotion without using shared storage, the contents of the virtual disk is transferred over the network as well.

Note:

vMotion network traffic is not encrypted. You should provision secure private networks for use by vMotion only.

Requirements for Concurrent vMotion Migrations

You must ensure that the vMotion network has at least 250Mbps of dedicated bandwidth per concurrent vMotion session. Greater bandwidth lets migrations complete more quickly. Gains in throughput resulting from WAN optimization techniques do not count towards the 250Mbps limit.

To determine the maximum number of concurrent vMotion operations possible, see the Concurrent migration limits at Limits on Simultaneous Migrations in the vSphere Web Client. These limits vary with a host's link speed to the vMotion network.

Metro vMotion

Some configurations include Metro vMotion, which is a feature that enables reliable migrations between hosts that are separated by high network round-trip latency times. Metro vMotion is enabled when the appropriate license is installed. No user configuration is necessary.

Multiple-NIC vMotion

You can configure multiple NICs for vMotion by adding two or more NICs to the required standard or distributed switch. For details, see the VMware knowledge base article at http://kb.vmware.com/kb/2007467.

Network Configuration

Configure the virtual networks on vMotion enabled hosts as follows:

  • On each host, configure a VMkernel port group for vMotion.

  • Ensure that virtual machines have access to the same subnets on source and destination hosts.

  • If you are using standard switches for networking, ensure that the network labels used for virtual machine port groups are consistent across hosts. During a migration with vMotion, vCenter Server assigns virtual machines to port groups based on matching network labels.

    Note:

    By default, you cannot use vMotion to migrate a virtual machine that is attached to a standard switch with no physical uplinks configured, even if the destination host also has a no-uplink standard switch with the same label.

    To override the default behavior, set the config.migrate.test.CompatibleNetworks.VMOnVirtualIntranet advanced setting of vCenter Server to false. The change takes effect immediately. For details about the setting, see VMware knowledge base article at http://kb.vmware.com/kb/1003832. For information about configuring advanced settings of vCenter Server, see Configure Advanced Settings in the vSphere Web Client.

  • If you are using vSphere Distributed Switches for networking, ensure that source and destination hosts are members of all vSphere Distributed Switches that virtual machines use for networking.

Best Practices for vMotion Networking

Recommended networking best practices are as follows:

  • Provide the required bandwidth in one of the following ways:

    • Dedicate at least one GigE adapter for vMotion.

      Use at least one 10 GigE adapter if you migrate workloads that have many memory operations.

      If only two Ethernet adapters are available:

      • For best security, dedicate the GigE adapter to vMotion, and use VLANs to divide the virtual machine and management traffic on the other adapter.

      • For best availability, combine both adapters into a bond, and use VLANs to divide traffic into networks: one or more for virtual machine traffic and one for vMotion.

    • Alternatively, direct vMotion traffic to one or more physical NICs that are shared between other types of traffic as well.

      • To distribute and allocate more bandwidth to vMotion traffic across several physical NICs, use multiple-NIC vMotion.

      • On a vSphere Distributed Switch 5.1 and later, use Network I/O Control shares to guarantee bandwidth to outgoing vMotion traffic. Defining shares also prevents from contention as a result from excessive vMotion or other traffic.

      • Use traffic shaping in egress direction on the vMotion port group on the destination host to avoid saturation of the physical NIC link as a result from intense incoming vMotion traffic. By using traffic shaping you can limit the average and peak bandwidth available to vMotion traffic, and reserve resources for other traffic types.

  • Provision at least one additional physical NIC as a failover NIC.

  • Use jumbo frames for best vMotion performance.

    Ensure that jumbo frames are enabled on all network devices that are on the vMotion path including physical NICs, physical switches and virtual switches.