A company has a server that runs Microsoft System Center Virtual Machine Manager (VMM)
2008 R2, System Center Data Protection manager (DPM) 2010, and Windows Server 2008
R2 with Hyper-V. A Hyper-V host has a virtual machine (VM) that uses a basic disk. You
need to perform a backup of the VM configuration and its virtual hard disk while minimizing
downtime. What should you do?
A.
Perform an offline backup by using DPM.
B.
Perform an online backup by using DPM.
C.
Perform a system state backup by using windows Server Backup.
D.
Perform a VMM database backup by using VMM.
Explanation:
Backing up Hyper-V
Host-Based Backups One exciting benefit of server virtualization is the prospect of no longer
having to individually back up the virtualized systems. Now that these systems are simply
files living on a host’s file system, you can just back up the files and call it a day, right? Not
exactly. Because these are live computers consisting of in-memory data, data on disk,
system configurations, and open files, there are a few things to consider. So how do we
ensure backup data consistency given all these moving parts?
A significant improvement to the Windows Server backup story came with Windows Server
2003 and the advent of VSS, which provides a standard set of extensible APIs that VSS
writers (hooks in applications and services that help provide consistent shadow copies) use
in order to create backups of open files and applications. With the help of the VSS service,
providers, and writers, the backup application can generate a point-in-time copy of a volume
very quickly, one that the application is aware of and can process appropriately. Hyper-V
comes with its own VSS writer that allows software makers to create compelling backup
solutions. The writer lets backup applications achieve host-based VSS backups of running
VMs. If the operating system running within the VM has the Hyper-V Integration Components
installed as well as the VSS service (available in Windows XP SP1 and Windows Server
2003 and later), the host-based backup will occur as if it were run inside the guest; the
backup will be performed with the VM running and the data will be consistent (see Figure
4).
Figure 4 VSS backup (Click the image for a larger view)
However, if the guest operating system does not support the Integration Components or
VSS, the backup process requires that the guest machine be put into a saved state and that
a host-based VSS snapshot is taken of VM data files that can be used for point-in-time
recovery. Saved-state VSS snapshots will incur some VM downtime (this can typically be
limited to 5-10 minutes), with full backup-to-tape procedures taking place against the VSS
copy of the data. Guest-Based Backups In a physical environment, servers and applications
need to be backed up on an individual basis, and such backups can certainly continue in a
virtualized datacenter. In this situation, the same considerations need to be taken into
account when backing up a VM, such as network capacity requirements for network-based
backups and performance impact to the system during the backup window. With guestbased
backups, you can choose to have a dedicated physical NIC in the host that is bound to a
virtual network that all guests use.
Windows Server Backup Included with Windows Server 2008 is the VSS-capable Windows
Server Backup (WSB), which can be used to perform Hyper-V host- and guest-based
backups of your VMs. Because it’s fully VSS-capable, it can perform host-based backups of
your running VMs, which of course is preferable.
But if you have VMs without the Integration Components installed, VSS will not be used. In
that case, you have a couple of options from which to choose. You can still use WSB to back
up a VM that does not have the Integration Components installed, which means the VM’s
state will be saved and then the backup will grab the VM’s virtual disks and configuration
files. However, this may not be desirable with an application such as Exchange because the
application will not be aware a backup has run and application logs will not be truncated.
Moreover, downtime will occur on the VM, which will vary depending on how long the backup
takes.
Alternatively, a backup can be run from inside the VM just as if it were a physical machine
using either NTBackup or WSB, depending on the VM’s OS. Let’s see how to use WSB for
supported guests that have the Integration Components installed.
Backing up VMs with WSB Hyper-V does not automatically register its VSS writer for use
with WSB. You must manually add the registry key and value shown in Figure 5 before WSB
will support a Hyper-V backup. You can add them via the command line, like so:Copy Code
reg add “HKLM\Software\Microsoft\windows nt\
currentversion\WindowsServerBackup\Application
Support\{66841CD4-6DED-4F4B-8F17-FD23F8DDC3DE}”
reg add “HKLM\Software\Microsoft\windows nt\
currentversion\WindowsServerBackup\Application
Support\{66841CD4-6DED-4F4B-8F17-FD23F8DDC3DE}” /v
“Application Identifier” /t REG_SZ /d Hyper-v
