Quiescing indicates pausing or altering the state of running processes on a computer, particularly those that might modify information stored on disk during a backup, to guarantee a consistent and usable backup.
For windows Microsoft VSS inside the guest will be used to quiesce the file system and applications. This ensures that the data consistency of the file system and all VSS supported applications. By default VMware will engage all of the VSS writers that are configured inside the guest. If it is necessary to exclude a writer please refer to http://kb.vmware.com/kb/1031200
For Linux, the vmsync driver will be used to quiesce the file system. This is included with VMware tools. The vmsync driver ensures that the file system is in a consistent state prior to the VMware snapshot being created. The vmsync driver is only supported with vSphere 5.0 and above.
Consider the following before enabling or disabling the quiescing during the backup:
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Hardware Snapshot with Quiescing - When you perform the IntelliSnap backup of a subclient, a hardware snapshot of all the virtual machines is created. Before the snapshot creation, the quiescing will be performed automatically for the operating system and applications on all the virtual machines in the subclient.
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Crash consistent hardware snapshot - The backup process may slow down because of the quiescing. If you do not want to perform quiescing before the snapshot creation, you can disable the quiescing. If you disable the quiescing, the crash consistent hardware snapshot will be created.
You can also perform an application aware backup as described in Application Aware Backups.
Follows the steps given below to disable quiescing:
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From the CommCell Console, navigate to Client Computers > virtualization_client > Virtual Server > VMware > backup_set.
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Right-click a subclient and click Properties.
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Click the Backup Options tab.
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Select Crash Consistent.
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Click OK.
When you perform the backup of a subclient, the quiescing will not be performed on all the virtual machines in the subclient.
Notes
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By default, when creating a snapshot on a VM, the file system and applications within the VM are quiesced. If the file system and applications cannot be quiesced, a non-quiesced snapshot is taken instead, and a warning is generated. When the requireSnapshotGuestFileSystem additional setting is configured on the VSA proxy with the value true, the automatic fall back to a non-quiesced snapshot is disabled and the backup of the VM fails.
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By default, quiesce guest errors cause jobs to complete with warnings. To ignore quiesce warnings for virtual machine backups, create the ignoreQuiesceGuestErrors additional setting on the Virtual Server Agent proxy and set the value to 1.