VMware 4817V62 - vSphere - PC, Administration Manual

Page: 193 / 364

Migrating Virtual Machines with Snapshots
Migration of virtual machines with snapshots is possible if the virtual machine resides on shared storage
accessible to source and destination hosts.
Some restrictions apply when migrating virtual machines with snapshots. You cannot migrate a virtual
machine with snapshots with Storage VMotion. Otherwise, migrating a virtual machine with snapshots is
permitted, regardless of the virtual machine power state, as long as the virtual machine is being migrated to
a new host without moving its configuration file or disks. (The virtual machine must reside on shared storage
accessible to both hosts.)
If the migration involves moving the configuration file or virtual disks, the following additional restrictions
apply:
n
The starting and destination hosts must be running ESX 3.5 or ESXi 3.5 or later.
n
All of the virtual machine files and disks must reside in a single directory, and the migrate operation must
move all the virtual machine files and disks to a single destination directory.
Reverting to a snapshot after migration with VMotion might cause the virtual machine to fail, because the
migration wizard cannot verify the compatibility of the virtual machine state in the snapshot with the
destination host. Failure occurs only if the configuration in the snapshot uses devices or virtual disks that are
not accessible on the current host, or if the snapshot contains an active virtual machine state that was running
on hardware that is incompatible with the current host CPU.
Migration with Storage VMotion
Using Storage VMotion, you can migrate a virtual machine and its disk files from one datastore to another
while the virtual machine is running.
You can choose to place the virtual machine and all its disks in a single location, or select separate locations
for the virtual machine configuration file and each virtual disk. The virtual machine does not change execution
host during a migration with Storage VMotion.
During a migration with Storage VMotion, you can transform virtual disks from thick-provisioned to thin-
provisioned or from thin-provisioned to thick-provisioned.
Storage VMotion has a number of uses in administering virtual infrastructure, including the following
examples of use:
n
Upgrading ESX/ESXi without virtual machine downtime. During an upgrade from ESX Server 2.x to
ESX/ESXi 3.5 or later, you can migrate running virtual machines from a VMFS2 datastore to a VMFS3
datastore, and upgrade the VMFS2 datastore without any impact on virtual machines. You can then use
Storage VMotion to migrate virtual machines back to the original datastore without any virtual machine
downtime.
n
Storage maintenance and reconfiguration. You can use Storage VMotion to move virtual machines off of
a storage device to allow maintenance or reconfiguration of the storage device without virtual machine
downtime.
n
Redistributing storage load. You can use Storage VMotion to manually redistribute virtual machines or
virtual disks to different storage volumes to balance capacity or improve performance.
Storage VMotion Requirements and Limitations
A virtual machine and its host must meet resource and configuration requirements for the virtual machine
disks to be migrated with Storage VMotion.
Storage VMotion is subject to the following requirements and limitations:
n
Virtual machines with snapshots cannot be migrated using Storage VMotion.
Chapter 16 Migrating Virtual Machines
VMware, Inc. 193