VM Data Processing

Backup from Storage Snapshots introduces a different mode of data processing for VMware VMs whose disks are located on storage volumes or LUNs.

Regular VM Data Processing

In the regular processing course, Veeam Backup & Replication uses a VMware snapshot as a source of data for backup and replication. The VMware snapshot “freezes” the VM state and data at a specific point in time. As a result, the VM data is brought to a consistent state suitable for backup.

During regular VM data processing, Veeam Backup & Replication performs the following actions:

1. Veeam Backup & Replication triggers a VMware snapshot for a VM. VM disks are put to the read-only state and every virtual disk of the VM receives a delta file named like vmname-00001.vmdk.
2. Veeam Backup & Replication copies VM data from read-only disks of the VM. All changes that the user makes to the VM while backup or replication is performed are written to delta files.
3. When VM processing is finished, the VMware snapshot is committed. VM disks resume writes, and data from delta files is merged to the VM disks. After data is merged, the VMware snapshot is removed.

Regular VM data processing may take long. If backup or replication is performed for a VM running a highly transactional application, the delta file may grow very large. As a result, the snapshot commit process will take much time, and the VM may even freeze during this process. To overcome this situation, you can use Backup from Storage Snapshots.

Backup from Storage Snapshots

Backup from Storage Snapshots lets you speed up backup and replication operations. For Backup from Storage Snapshots, Veeam Backup & Replication complements the VMware snapshot technology with snapshots on storage systems and uses storage snapshots as a source of data for backup and replication.

During Backup from Storage Snapshots, Veeam Backup & Replication performs the following actions:

1. Veeam Backup & Replication triggers a VMware snapshot for VMs whose disks are located on storage volumes or LUNs.
2. Veeam Backup & Replication triggers a storage snapshot of the volume or LUN holding the VM itself and the created VMware snapshot.
3. The VMware snapshot on the original storage volume is deleted immediately after the storage snapshot is created. To copy VM data, Veeam Backup & Replication accesses the ‘cloned’ VMware snapshot on the storage snapshot.
4. When VM processing is finished, the storage snapshot capturing the VMware snapshot is removed.

As a result, the VMware snapshot exists for a very short time — for several seconds. Delta files do not grow large and the time of VMware snapshot commit decreases up in several times.