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NetVault Plug-in for VMware 13.2.1 - User Guide

Introducing NetVault Plug-in for VMware Installing the plug-in Configuring the plug-in Defining a backup strategy Using the image-level backup method Using the file-level backup method Restoring image-level backups Restoring file-level backups Troubleshooting

Enabling or disabling quiescing of virtual machines

This section includes the following topics:

•
About quiescing virtual machines
•
Enabling quiescing of virtual machines
•
Disabling quiescing of virtual machines
•
Removing backup preferences for a virtual machine

About quiescing virtual machines

A virtual machine can be quiesced to create consistent snapshots for backups. Quiescing is performed using the VMware VSS component, which is provided with VMware Tools. The VMware VSS component is automatically installed when you install VMware Tools on the virtual machines.

Quiescing is only supported on Windows-based virtual machines. You can enable or disable quiescing of virtual machines.

Depending on the quiescing method used, the plug-in generates the following types of snapshots:

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Crash-consistent snapshots: Crash-consistent snapshots capture the volume state as it would be after a power outage. Such snapshots are not guaranteed to be free of incomplete I/O operations or data corruption. During a restore, there can be some data loss or corruption that can cause application failure.
 
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NOTE: On Linux-based virtual machines, the plug-in always generates crash-consistent snapshots. You can install the VMware SYNC driver on Linux-based systems to freeze and thaw filesystem I/O and obtain a consistent snapshot that reduces the risk of data loss and data corruption after restore. However, creating quiesced snapshots using SYNC driver requires waiting for I/O to drain in the Guest OS. This activity can affect time-sensitive applications.
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File-system-consistent snapshots: For file-system-consistent snapshots, all file system I/O is temporarily frozen and dirty memory data is flushed to the disk before the snapshot is taken.
To create file-system-consistent snapshots, you must install the VMware VSS component on the virtual machines as part of VMware Tools.
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VSS-based application-consistent snapshots: For application-consistent snapshots, all application data in memory is written to the disk. Application-consistent snapshots reduce the amount of application-crash recovery that you must perform for VSS-enabled applications, such as SQL Server, Exchange, and SharePoint, after restoring an image-level backup.
To create application-consistent snapshots, the following requirements must be met:
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You must install the VMware VSS component on the virtual machines as part of VMware Tools.
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The virtual machines should only use SCSI disks. Application-consistent snapshots are not supported on virtual machines that use IDE disks or dynamic disks.
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The virtual machines should have enough free SCSI slots as the number of disks.

Enabling quiescing of virtual machines

Quiescing is only supported on Windows-based virtual machines. You can set the backup preferences to enable quiescing for all or specific virtual machines.

1
Start the Backup Job Wizard, and click next to the Selections list.
2
Open the NetVault Client on which plug-in is installed, and then open VMware Plugin.
3
To enable quiescing for all virtual machines managed by an ESXi or vCenter Server, click the server, and select Set Backup Preferences from the context menu.
To enable quiescing for specific virtual machines, open the ESXi or vCenter Server and the other applicable container nodes — for example, Datacenter, Cluster, Resource Pool, and other nodes — to display the target virtual machines. Click the virtual machine, and select Set Backup Preferences from the context menu.
4
In the Backup Preferences dialog box, select the Quiesce VM for snapshot option.
This check box is cleared by default. To quiesce a virtual machine before creating a snapshot, select this check box. The setting for an individual virtual machine level takes precedence over the server-level setting.
5
To close the dialog box, click OK.

Disabling quiescing of virtual machines

On virtual machines with high processor or IO load, the quiesce operation may timeout and cause the backup job to fail. In such cases, you can disable quiescing for all or specific virtual machines. When you disable quiescing, the plug-in uses crash-consistent snapshots to perform backups.

1
Start the Backup Job Wizard, and click next to the Selections list.
2
Open the NetVault Client on which plug-in is installed, and then open VMware Plugin.
3
To disable quiescing for all virtual machines managed by an ESXi or vCenter Server, click the server, and select Set Backup Preferences from the context menu.
To disable quiescing for specific virtual machines, open the ESXi or vCenter Server and the other applicable container nodes — for example, Datacenter, Cluster, Resource Pool, and other nodes — to display the target virtual machines. Click the virtual machine, and select Set Backup Preferences from the context menu.
4
In the Backup Preferences dialog box, clear the Quiesce VM for snapshot option.
Clearing this check box creates a snapshot without quiescing a virtual machine. The setting for an individual virtual machine level takes precedence over the server-level setting.
5
To close the dialog box, click OK.
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