Active Full Backup and Synthetic Full Backup in Veeam essentially serve the same purpose: creating a full backup file containing the data of the entire virtual machine (VM). However, they differ significantly in how they do this and, consequently, their impact on the system.
Here are the definitions and differences between these two backup types:
What is Active Full Backup?
Active Full is the traditional full backup method.
- Data Source: Reads data directly from the source data store where the virtual machine (VM) is located.
- Process: Veeam Backup & Replication retrieves all VM data from the source, compresses and deduplicates it, then writes it to the backup repository as a new .vbk (full backup) file.
- Areas of Influence:
- Production Environment (Source): The load on the source datastore and VM where the VM is located will be high because all the data needs to be read.
- Network Resources: Network bandwidth is intensive as all data must be transferred from the source datastore to the backup store.
- Backup Storage (Target): The load is limited to data write operation only.
What is Synthetic Full Backup?
Synthetic Full is a more modern approach that creates a full backup file from existing backup files.
- Data Source: It doesn't read data from the source data store where the virtual machine resides. Instead, it uses the previous full backup file already in the backup store and the incremental backup files made up to that point.
- Process: Veeam synthesizes a new full backup (.vbk) file representing the current state of the VM by combining the data from these existing files in the backup repository.
- Areas of Influence:
- Production Environment (Source): The load is very low because only enough data is read from the source to take the last incremental backup (i.e. only the data that has changed).
- Network Resources: Network bandwidth usage is low since only a small incremental amount of data is received from the source.
- Backup Repository (Target): Since the entire merging and synthesis process takes place in the backup repository, the I/O (read/write) load on the repository is high.
Main Differences Between Active Full and Synthetic Full
| Feature | Active Full Backup | Synthetic Full Backup |
| Data Source | Direct source VM datastore. | Current full and incremental backups in the backup repository |
| Load on the Production Environment | High because all data must be read. | Very low as only the last incremental data needs to be read |
| Network Bandwidth | Intensive use as all data must be transferred | Low usage as only incremental data needs to be transferred |
| Backup Storage Load | Only the overhead of writing new data (Write) | The overhead of reading existing backups and writing the combined new full backup (Read/Write) is high |
| Creation Time | It usually takes longer (depending on the transfer of data over the network). | Total backup time may be reduced due to reduced network traffic, but it depends on the performance of the repository. |
| Usage Scenario | It provides the most reliable way to start a new backup chain. It may be preferred if the network is slow and the repository is fast. | Provides minimal load on the production environment. If the network is fast and the repository is slow, it may struggle. |
Which is Preferred in Which Situation?
If you want to minimize the load on your production environment (the servers and disks where VMs run) and reduce network usage. Synthetic Full is preferred, especially if you're using file systems that support Fast Clone technologies like ReFS or XFS. Synthetic Full is preferred because it completes the backup repository almost instantly and uses very little disk space.
If your backup repository disks are slow and you don't want the defragmentation process to take too long. Or if you want to periodically start a new, completely independent backup chain to verify backup integrity from the beginning, Active Full is preferred.
Listing Active and Synthetic Full Status in Veeam Backup Jobs
Veeam Backup & Replication simplifies backup processes with its powerful features. With PowerShell, you can take things a step further and automate and customize daily operations!
The PowerShell script below provides a list of which backup jobs in Veeam Backup & Replication are Active Full, which are Synthetic Full, and which are Full on which day.
Get-VBRJob | where {$_.IsScheduleEnabled -eq $True} | where {$_.JobType -eq "Backup"} | select -Property @{N="Name";E={$_.Name}},
@{N="Active Full Enabled";E={$_.BackupStorageOptions.EnableFullBackup}},
@{N="Synthetic Full Enabled";E={$_.BackupTargetOptions.TransformFullToSyntethic}},
@{N="Full Backup Days";E={$_.BackupTargetOptions.FullBackupDays}} | Sort-Object "Full Backup Days" | ft -AutoSize
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