Configuring VMware vMotion
The VMware VMotion feature, part of VirtualCenter, allows you to migrate running virtual machines from one physical machine to another with no perceivable impact to the end user (Figure 1). You can use VMotion to upgrade and repair servers without any downtime or disruptions and also to optimize resource pools dynamically, resulting in an improvement in the overall efficiency of a data center. To ensure successful migration and subsequent functioning of the virtual machine, you must respect certain compatibility constraints. Complete virtualization of all components of a machine, such as CPU, BIOS, storage disks, networking, and memory, allows the entire state of a virtual machine to be captured by a set of data files. Therefore, moving a virtual machine from one host to another is nothing but data transfer between two hosts.
Figure 1: VMware vMotion Enables Virtual Machine Mobility
VMware vMotion benefits data center administrators in critical situations, such as:
- Hardware maintenance: VMotion allows you to repair or upgrade the underlying hardware without scheduling any downtime or disrupting business operations.
- Optimizing hardware resources: VMotion lets you move virtual
machines away from failing or underperforming hosts.
- This can be done automatically in combination with VMware Distributed Resource Scheduler (DRS). VMware DRS continuously monitors utilization across resource pools and allocates resources among virtual machines based on current needs and priorities. When virtual machine resources are constrained, DRS makes additional capacity available by migrating live virtual machines to a less‐utilized host using VMotion.
The requirements for vMotion include:
- Datastore compatibility: The source and destination hosts must use shared storage. You can implement this shared storage using a SAN or iSCSI. The shared storage can use VMFS or shared NAS. Disks of all virtual machines using VMFS must be available to both source and target hosts.
- Network compatibility: VMotion itself requires a Gigabit Ethernet network. Additionally, virtual machines on source and destination hosts must have access to the same subnets, implying that network labels for each virtual Ethernet adapter should match. You should configure these networks on each ESX host.
- CPU compatibility: The source and destination hosts must have compatible sets of CPUs.
VMware vMotion is configured on all MetaFabric 1.0 hosts (Figure 2). VMware vMotion is using a separate port group called PG-vMotion-106, and VMkernel is bound to this port group. Network and storage is unique on all hosts, which is a requirement for vMotion. Once vMotion configuration is completed, active VMs will be moved any available host where resources are free. DRS can also kick in the vMotion feature if one of the ESX hosts shows high resource utilization (CPU, memory). You can also manually trigger vMotion if the need arises to move a VM within the data center.
Figure 2: VMware vMotion Configured in the Test Lab
For more information on configuration of VMware vMotion, see:
Creating a VMkernel port and enabling vMotion on an ESXi/ESX host
