Windows Server 2008 R2 Unleashed (303 page)

Image rollback has been successfully used for training purposes where an employee runs

through a process, then rolls back the image so they can run through the same process all

over again repeating the process on the same base image but without previous installa-

tions or configurations.

In network infrastructures, a snapshot is helpful when an organization applies a patch or

update to a server, or a software upgrade is performed and problems occur; the administrator

can simply roll back the image to the point prior to the start of the upgrade or migration.

Snapshots for Guest Session Server Fault Tolerance

Snapshots are commonly used in business environments for the purpose of fault tolerance

or disaster recovery. A well-timed snapshot right before a system failure can help an orga-

nization roll back their server to the point right before the server failed or problem

occurred. Rather than waiting hours to restore a server from tape, the activation of a snap-

shot image is nothing more than choosing the snapshot and selecting to start the guest

image. When the guest image starts up, it is in the state that the image was at the time the

snapshot was created.

Creating a Snapshot of a Guest Image

Snapshots are very easy to create. To create a snapshot, do the following:

1. From the Server Manager console or from the Hyper-V Manager MMC snap-in, click

to select the guest session for which you want to create a snapshot.

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2. Right-click the guest session name, and choose Snapshot. A snapshot of the image

will immediately be taken of the guest image and the snapshot will show up in the

Snapshots pane, as shown in Figure 37.8.

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FIGURE 37.8

Snapshot of a running Hyper-V guest session.

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Rolling Back a Guest Image to a Previous Snapshot Image

The term used in Windows Server 2008 R2 Hyper-V to roll back an image is called “apply-

ing” a snapshot to an existing image. When an image is rolled back, the image that is

currently running has the snapshot information applied to the image, thus bringing the

image back to an earlier configuration state. To apply a snapshot, do the following:

1. From the Server Manager console or from the Hyper-V Manager MMC snap-in, click

the snapshot to which you want to revert the running guest image.

2. Right-click the snapshot image and choose Apply. The configuration state of the image

will immediately be reverted to the state of the image when the snapshot was taken.

NOTE

By default, the name of the snapshot image takes on the date and time the image was

created. As an example, if the virtual machine is called “Windows 2008 R2 IIS,” an

image taken on September 2, 2009 at 9:42 p.m. would show up as “Windows 2008

R2 IIS - (9/2/2009 - 9:42:22 PM).” Snapshots can be renamed to something more

meaningful, if desired, such as “Clean Build with All Patches”.

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Reverting a Snapshot Session

When working with snapshots, if you snapshot a session, the revert action can be used on

the virtual machine to revert the guest session’s state to the last created or applied snap-

shot. All changes since the last creation or application of a snapshot will be discarded.

Quick Migration and Live Migration

There are two forms of automated migration provided by Windows Server 2008 R2 Hyper-

V: Quick Migration and Live Migration. These migration processes can be used to increase

service availability for planned and unplanned downtime.

Although both technologies achieve the same thing—moving virtual servers between

Hyper-V hosts—they use different methods and mechanisms to achieve it. Both require at

least two Hyper-V host servers in a cluster, attached to the same shared storage system.

Usually, the shared storage is an iSCSI or Fibre Channel storage area network (SAN).

Quick Migration

Quick Migration provides a way to quickly move a virtual machine from one host server

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to another with a small amount of downtime.

In a Quick Migration, the guest virtual machine is suspended on one host and resumed on

another host. This operation happens in the time it takes to transfer the active memory of

the virtual machine over the network from the first host to the second host. For a host

with 8GB of RAM, this might take about two minutes using a 1GB iSCSI connection.

Quick Migration was the fastest migration available for Windows Server 2008 Hyper-V.

Microsoft made considerable investments in Hyper-V migration technologies, trying to

reduce the time required to migrate virtual machines between Hyper-V hosts. The result

was Live Migration, which has the same hardware requirements as Quick Migration, but

with a near instantaneous failover time.

Live Migration

Since the release of Hyper-V V1 with Windows Server 2008, the number-one most-

requested feature by customers is the ability to migrate running virtual machines between

hosts, with no downtime. VMware’s VMotion has been able to do this for some time.

Finally, with Windows Server 2008 R2, it can be done natively with Hyper-V for no extra

cost. This makes it a compelling reason to move to Hyper-V.

Live Migration uses failover clustering. The quorum model used for your cluster will

depend on the number of Hyper-V nodes in your cluster. In this example, we will use two

Hyper-V nodes in a Node and Disk Majority Cluster configuration. There will be one

shared storage LUN used as the cluster quorum disk and another used as the Cluster

Shared Volume (CSV) disk, described later in this chapter. For more details on clustering,

see Chapter 29, “System-Level Fault Tolerance (Clustering/Network Load Balancing).”

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NOTE

If there is only one shared storage LUN available to the nodes when the cluster is

formed, Windows will allocate that LUN as the cluster quorum disk and it will not be

available to be used as a CSV disk.

This section describes how to use Hyper-V Live Migration to move virtual machines

between clustered Hyper-V hosts.

Configuring the Cluster Quorum Witness Disk

Live Migration requires a Windows Server 2008 R2 cluster configured to use shared

storage. Typically, these are LUNs provisioned on an iSCSI or Fibre Channel SAN. One

LUN will be used as the witness disk for quorum and another will be used as a Cluster

Shared Volume (CSV) to store the virtual machine images. The CSV will be configured

later in this chapter.

The LUN for the shared witness quorum disk must be configured before the cluster is

formed, so that cluster manager can configure the cluster properly. Connect this LUN via

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iSCSI or Fibre Channel to both nodes you will use for the cluster. The disk must be initial-

ized and formatted with an NTFS file format prior to cluster use. When properly config-

ured, both nodes share the same online Basic disk and can access the disk at the same time.

IMPORTANT

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The Windows cluster service will always use the first shared disk as the cluster quorum

disk. Provision this disk first on each node.

Now that the shared storage witness disk has been configured, we can move on to

installing the Windows cluster.

Installing the Failover Clustering Feature

Before a failover clustering can be deployed, the necessary feature must be installed. To

install the Failover Clustering feature, perform the following steps:

1. Log on to the Windows Server 2008 R2 cluster node with an account with adminis-

trator privileges.

2. Click the Server Manager icon in the Windows taskbar.

3. Select the Features node in the tree pane when Server Manager opens.

4. In the tasks pane, select the Add Features link.

5. In the Select Features window, select Failover Clustering, click Next, and click Install

on the Confirm Installation Selections page to install the feature.

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6. When the installation completes, click Close to complete the installation and return

to Server Manager.

7. Close Server Manager and install the Failover Clustering feature on each of the

remaining cluster nodes.

Running the Validate a Configuration Wizard

Failover Cluster Management is used to administer the Failover Clustering feature. It can

be run from Server Manager or as a separate MMC console. After the feature is installed,

run the Validate a Configuration Wizard from the tasks pane of the Failover Cluster

Management console. All nodes should be up and running when the wizard is run. To run

the Validate a Configuration Wizard, perform the following steps:

1. Log on to one of the Windows Server 2008 R2 cluster nodes with an account with

administrator privileges over all nodes in the cluster.

2. Click Start, click All Programs, click Administrative Tools, and select Failover Cluster

Management.

3. When the Failover Cluster Management console opens, click the Validate a

Configuration link in the Actions pane.

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4. When the Validate a Configuration Wizard opens, click Next on the Before You

Begin page.

5. On the Select Servers or a Cluster page, enter the name of a cluster node, and click

the Add button. Repeat this process until all nodes are added to the list, as shown in

Figure 37.9, and click Next to continue.

FIGURE 37.9

Adding the servers to be validated by the Validate a Configuration Wizard.

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6. On the Testing Options page, read the details that explain the requirements for all

tests to pass in order to be supported by Microsoft. Select the Run All Tests

(Recommended) option button, and click Next to continue.

7. On the Confirmation page, review the list of servers that will be tested and the list

of tests that will be performed, and click Next to begin testing the servers.

NOTE

For years, administrators have complained that the Validate a Configuration Wizard win-

dow is too small. In Windows Server 2008 R2, administrators can finally resize the win-

dow by dragging the lower-right corner. This is not obvious, but try it—it works!

8. When the tests complete, the Summary page displays the results, and if the tests

pass, click Finish to complete the Validate a Configuration Wizard. If the tests failed,

click the View Report button to review the details and determine which test failed

and why the test failed.

Even if the Validate a Configuration Wizard does not pass every test, depending on the

test, creating a cluster might still be possible. After the Validation a Configuration Wizard

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is completed successfully, the cluster can be created.

Creating a Node and Disk Majority Cluster

When the failover cluster is first created, all nodes in the cluster should be up and

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running. To create the failover cluster, perform the following steps:

1. Log on to one of the Windows Server 2008 R2 cluster nodes with an account with

administrator privileges over all nodes in the cluster.

2. Click Start, click All Programs, click Administrative Tools, and select Failover Cluster

Management.

3. When the Failover Cluster Management console opens, click the Create a Cluster