Datasheet

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EXPLORING VMWARE VSPHERE 5
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Figure 1.2
vSphere Virtual
SMP allows VMs
to be created with
more than one
virtual CPU.
VMkernel
Virtual SMP
VSPHERE VMOTION AND VSPHERE STORAGE VMOTION
If you have read anything about VMware, you have most likely read about the extremely
useful feature called vMotion. vSphere vMotion, also known as live migration, is a feature of
ESXi and vCenter Server that allows an administrator to move a running VM from one physical
host to another physical host without having to power off the VM. This migration between two
physical hosts occurs with no downtime and with no loss of network connectivity to the VM.
The ability to manually move a running VM between physical hosts on an as-needed basis is a
powerful feature that has a number of use cases in today’s datacenters.
Suppose a physical machine has experienced a non-fatal hardware failure and needs to be
repaired. Administrators can easily initiate a series of vMotion operations to remove all VMs
from an ESXi host that is to undergo scheduled maintenance. After the maintenance is complete
and the server is brought back online, administrators can utilize vMotion to return the VMs to
the original server.
Alternately, consider a situation in which you are migrating from one set of physical serv-
ers to a new set of physical servers. Assuming that the details have been addressed—and I’ll
discuss the details around vMotion in Chapter 12, “Balancing Resource Utilization”—you can
use vMotion to move the VMs from the old servers to the newer servers, making quick work of a
server migration with no interruption of service.
Even in normal day-to-day operations, vMotion can be used when multiple VMs on the same
host are in contention for the same resource (which ultimately is causing poor performance
across all the VMs). vMotion can solve the problem by allowing an administrator to migrate any
VMs that are facing contention to another ESXi host with greater availability for the resource in
demand. For example, when two VMs are in contention with each other for CPU resources, an
administrator can eliminate the contention by using vMotion to move of one of the VMs to an
ESXi host that has more available CPU resources.
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