VMware HotAdd backups

For Unitrends Backup appliances that are deployed on VMware, Unitrends recommends that you configure backups to use the HotAdd transport mode for ESX hosts whose datastores are located on an external SAN. This configuration enables the appliance to move data directly from the external SAN to the appliance during the backup. This direct connection increases backup performance and decreases network bandwidth utilization, affording greater scheduling flexibility as the production network is not used during the backup.

See the following topics to set up HotAdd backups:

In addition to the Best practices and requirements for VMware protection, these requirements must be met to run VMware backups using the HotAdd transport mode:

• The Unitrends appliance must be a Unitrends Backup on VMware appliance. (For Recovery Series and Recovery MAX appliances, use the SAN-direct feature instead. See VMware SAN-direct backups for details.)
• Both the Unitrends Backup VM and the VMs to protect must be running in an ESXi environment with the following storage configurations:
– SAN storage mounted on the ESXi server as a VMFS datastore.
– SAN storage mounted directly by the ESXi guest as a virtual RDM disk.

Other storage configurations, such as VSANs and VVoL datastores, are not supported.

• Both the Unitrends Backup VM and the VMs to protect must be added to the ESXi host through a vCenter. Directly adding a VM to the ESXi host is not supported.
• The VMware vSphere version must either be version 5.1 or later, or 5.0 with an advanced license that supports the HotAdd feature. (See VMware documentation for details.)
• The HotAdd transport mode can be used for all guest operating system versions.
• The HotAdd transport mode cannot be used to protect VMware templates.
• Do not use the HotAdd transport mode to protect Linux VMs configured with Logical Volume Manager (LVM) disks.

Important!  If your datastores are located on SAN LUNs, work with Unitrends Support to disable the HotAdd feature on the appliance itself to ensure the HotAdd transport mode is not used for backups of your LVM disks.

• For optimal performance, it is recommended to use VAAI-compatible storage arrays with the HotAdd feature.

For non-VAAI storage arrays, the ESXi host may perform certain operations on the datastore while the HotAdd backup is running, causing a SCSI reservation conflict. In this case, the backup continues over the network instead of the SAN, which increases both backup time and network traffic on the LAN. To reduce the probability of reservation conflicts, follow VMware’s recommendations in the article Frequently Asked Questions for vStorage APIs for Array Integration (1021976).

Note:  No configuration of the Unitrends storage subsystem is required. All configuration is done in the VMware and SAN environments.

1 Configure the ESXi server(s) to access the datastore(s) on the SAN LUNs.

In clustered environments, all ESXi servers in the cluster must be configured to access the datastores.

2 Physically connect the ESXi host machine to the SAN using an iSCSI or Fibre Channel cable.
3 Run backups for the guest VMs as described in To create a VMware backup job.

The appliance detects the SAN storage configuration and uses the HotAdd transport method during backup.

Notes:   

• If the appliance cannot directly access the SAN, the backup runs using the network connection, moving the guest’s data from the external SAN through the ESXi file system to the backup appliance. If using network bandwidth is a problem during certain hours, schedule your backups accordingly.
• Note that when recovering HotAdd backups, VMware determines the most efficient transport method. Data is usually restored directly to the ESXi server as the VMFS datastore must be utilized.
4 After running the first HotAdd backup, view backup details to verify that the HotAdd transport method was used. View details by doing one of the following:
• Click Jobs > Recent Jobs, select the job and click View Log. Look for the transport method in the Output area.

• Click Reports > Backup > Backup History. Run the report by entering a date range and clicking Generate Report. Select the job and look for the transport method in the Output area in the Backup Status Report Entry dialog.

The transport method message indicates whether the HotAdd method was used:

• using transport method hotadd indicates the HotAdd transport mode was used for the backup.
• using transport method nbd or using transport method nbdssl indicates the regular network connection was used for the backup. Check your physical cable connection and the iSCSI or FC configuration for issues.