When you run a synthetic full backup from a subclient or schedule a synthetic full backup when running the job interactively, the software initiates individual synthetic full backup jobs for each VM in the subclient. A VM Admin (synthetic full) job is created only after the synthetic full job completes for at least one VM.
If necessary, you can run incremental backups in parallel with synthetic full backups.
Note
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When a VM has run a recent full backup job, Commvault software does not run a synthetic full backup job.
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If a synthetic full backup job is initiated by an automatic backup schedule that is associated with a subclient, only the child jobs for each VM run, and no VM Admin (synthetic full) job is created for the subclient. The system staggers automatic synthetic full backups at the VM level. This eliminates the need to have a parent synthetic full backup job, because VM jobs may run at different times due to the staggering.
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For virtualization clients that are configured for VM-centric operations, if you associate child VMs with a schedule policy that initiates synthetic full backups, the synthetic full backup jobs are only visible from the job history for the child VMs or when you view jobs for the schedule policy. Synthetic full backup jobs appear in the job history for the subclient only if the virtualization client or subclient are associated with the schedule policy.
Multi-Stream Synthetic Full Backups
VM-centric synthetic full backup operations always use multiple streams and initiate synthetic full operations for multiple VMs at the same time. Also, you can initiate a synthetic full backup operation for an individual VM. A synthetic full backup operation for an individual VM will always use only one stream, even if you select the Use Multiple Streams option.
Multi-stream synthetic full backup operations always use data from the latest backup cycle, from the most recent full backup through the most recent incremental backup. The synthetic full backup operation begins when the most recent backup operation for the subclient is complete.
You can initiate a new incremental backup operation while a synthetic full backup is in progress, but data from the new incremental backup is not included in a synthetic full backup that is already in progress.
If any volumes are not available during the synthetic full backup operation, the process skips those volumes and then retries them later in the process.
Note
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You can initiate a synthetic full backup operation for a specific VM.
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If you run a synthetic full backup operation immediately (without using a schedule), or using an existing schedule that does not have the Use Multiple Streams option set, the operation automatically uses multiple streams. VSA V2 synthetic full jobs run directly on the VM level, and each job uses one stream by default.
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When multi-stream synthetic full backups are enabled, each VM can use a separate stream. A single VM backup does not use multiple streams.
Procedure
For the complete list of steps, see Creating a Schedule Policy for Synthetic Full Backups with Multiple Streams.
The following options apply for VSA synthetic full backup operations:
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For the Agent Type in the schedule policy, select Virtual Server.
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VSA V2 synthetic full jobs run directly on the VM level, and each job uses one stream by default.