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Druva interacts with VMware components to back up applications running inside a virtual machine. The following steps describe how Druva backs up Microsoft SQL Server databases inside a VM. Druva utilizes Microsoft VSS and SQL Writer service to back up SQL Server databases inside a virtual machine. Druva requires virtual machine credentials to perform application-aware backups.
Ensure that you provide the VM credentials to Druva when you configure application-aware backups on virtual machines.
Step 1
Virtual machine backup request is initiated based on,
Schedule defined in the backup policy.
Manual backup
Druva forwards the backup request to the backup proxy pool.
The backup proxy queries the ESXi hypervisor or the vCenter server to create VM recovery points that contain VMDK files and the VMX files of the virtual machines. Ensure that enough storage is available on the local datastore for the VM recovery point.
The backup proxy uses CBT and Tools Quiescing to create a virtual machine recovery point. For the first automatic backup, the backup proxy creates a recovery point of a full backup. For all subsequent backups, the backup proxy creates recovery points of the incremental backups.
Backup proxy establishes a VDDK connection to the VM recovery point using a transport mode to read the VM data.
Reading encrypted VMDK through the NBD mode is not supported. The backup proxy can read encrypted VMDK disks either using NBDSSL or HotAdd. Here are the supported transport modes:
Encrypted backup proxy:
For encrypted virtual machine the supported transport mode is HotAdd.
For unencrypted virtual machine the supported transport mode is HotAdd.
Unencrypted backup proxy:
For encrypted virtual machine the supported transport mode is NBD-SSL.
Backup proxy transfers the backup data in a continuous stream to the Druva Cloud. Before transferring the data to the Druva Cloud, the backup proxy performs the de-duplication.
After the transfer completes, the backup proxy deletes the recovery point stored on the local datastore.
After the backup proxy uploads the virtual machine backup to the Druva Cloud, it performs the following steps:
In addition to the full SQL Server database backup, Druva supports transaction log backup of the databases to provide a tighter recovery point objective (RPO). The following workflow describes how Druva backs up transaction logs of the SQL Server databases on the virtual machines for which the backup proxy runs SQL Server aware backups.
Transaction log backup requires successful SQL Server aware virtual machine backups.
The backup policy initiates a transaction log backup request. Druva forwards the backup request to the backup proxy pool.
Note: Since the SQL Server executable copies the transaction logs to the <PATH> on the virtual machine, the process can cause storage consumption bloat.
After the backup proxy uploads the transaction logs to the Druva Cloud, it performs the following steps:
The Druva backup proxy starts from step 1 when the next log backup schedule kicks in. For example, you specified an interval of 30 minutes. If the full virtual machine SQL Server aware backup got completed at 12:00 PM, the first log backup happens at 12:00 PM. If the first log backup completes at 12:20 PM, the next log backup starts according to the schedule at 12:30 PM. If the first log backup runs until 12:45 PM, the next log backup starts immediately as soon as the current log backup ends. The Druva backup proxy continues backing up transaction logs until the next full SQL Server aware VM backup runs.
To know more about virtual machine backup, see Backup and Restore VMware Virtual Machines.
If you observe the below error in your Windows event logs, contact Druva Support:
Event ID: 57 NTFS Warning The system failed to flush data to the transaction log. Corruption may occur. Event ID: 137 NTFS Error The default transaction resource manager on volume \\?\Volume{806289e8-6088-11e0-a168-005056ae003d} encountered a non-retryable error and could not start. The data contains the error code. Event ID: 140 NTFS Warning The system failed to flush data to the transaction log. Corruption may occur in VolumeId:<> DeviceName: \Device\HarddiskVolume<>.(A device which does not exist was specified.).Few databases might not be recoverable since the VSS service failed to keep the SQL VSS recovery point persistent on the source VM. Druva is working closely with VMware support to address the above problem.