VMware vSphere vCenter Server 4.0 - Manual (Page 57)

Procedure
1 Select the host and select Enter Maintenance Mode from the right-click menu.
2 After the host is in maintenance mode, drag it to a different inventory location, either the top-level
datacenter or a different cluster.
When you move the host, its resources are removed from the cluster. If you grafted the host’s resource
pool hierarchy onto the cluster, that hierarchy remains with the cluster.
After you move the host, you can:
n Remove the host from vCenter Server. (Select Remove from the right-click menu.)
n Run the host as a standalone host under vCenter Server. (Select Exit Maintenance Mode from the right-
click menu.)
n Move the host into another cluster.
Using Maintenance Mode
You place a host in maintenance mode when you need to service it, for example, to install more memory. A
host enters or leaves maintenance mode only as the result of a user request.
Virtual machines that are running on a host entering maintenance mode need to be migrated to another host
(either manually or automatically by DRS) or shut down. The host is in a state of Entering Maintenance
Mode until all running virtual machines are powered down or migrated to different hosts. You cannot power
on virtual machines or migrate virtual machines to a host entering maintenance mode.
When no more running virtual machines are on the host, the host’s icon changes to include under
maintenance and the host’s Summary panel indicates the new state. While in maintenance mode, the host does
not allow you to deploy or power on a virtual machine.
N
OTE
DRS does not recommend (or perform, in fully automated mode) any virtual machine migrations off
of a host entering maintenance or standby mode if the VMware HA failover level would be violated after the
host enters the requested mode.
Using Standby Mode
When a host machine is placed in standby mode, it is powered off.
Normally, hosts are placed in standby mode by the VMware DPM feature to optimize power usage. You can
also place a host in standby mode manually. However, DRS might undo (or recommend undoing) your change
the next time it runs. To force a host to remain off, place it in maintenance mode and power it off.
Removing Virtual Machines from a Cluster
You can remove virtual machines from a cluster.
You can remove a virtual machine from a cluster in two ways:
n When you remove a host from a cluster, all of the powered-off virtual machines that you do not migrate
to other hosts are removed as well. You can remove a host only if it is in maintenance mode or disconnected.
If you remove a host from a DRS cluster, the cluster can become yellow because it is overcommitted.
n You can migrate a virtual machine from a cluster to a standalone host or from a cluster to another cluster
using the Migrate Virtual Machine wizard. To start this wizard either drag the virtual machine object on
top of the cluster object or right-click the virtual machine name and select Migrate.
If the virtual machine is a member of a DRS cluster rules group, vCenter Server displays a warning before
it allows the migration to proceed. The warning indicates that dependent virtual machines are not
migrated automatically. You have to acknowledge the warning before migration can proceed.
Chapter 6 Using DRS Clusters to Manage Resources
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