Understanding ABDs

Categories: ABDs, XenServer, Enhanced jobs, Backup, Replication, FAQs, Alike v4


The ABD (Alike Backup Delegate) is only required on XenServer platforms, and provides the “Enhanced” backup/replication features, as well as restore operations. ABDs run as tiny virtual appliances, and are dynamically provisioned by Alike from a template only when needed, and they are disposed of when their work is complete. The ABD template is a tiny (~128MB) virtual appliance image that Alike deploys and manages in your XenServer pool, as a hidden template.

In XenServer pooled environments, the ABD template must reside on shared storage, which must be accessible by all hosts in a resource pool. For environments with multiple pools, one template image must be deployed to the shared storage of each pool. In single XenServer host environments, you may deploy your ABD image to local storage.

Alike will automatically deploy your ABD templates during the initial installation wizard. However, when introducing new Xen pools to Alike, you may need to ask Alike to deploy a new template. Alike will automatically select the best SR for your ABD template. If for some reason you wish to store your ABD template on a different SR, you may simply migrate the ABD template’s disks in XenCenter, and Alike will automatically detect its new location.

ABD Networking

When Alike provisions an ABD to use for a backup, replication, or restore job, it will create a temporary VM from the template. Once booted, Alike will assign (or request via DHCP) an IP for the ABD. Each ABD will require an IP to function during its operation. If you plan on using multiple ABDs, you must either assign sufficient IP addresses manually, or ensure your DHCP pool has enough spare IPs to lease out.

By default, Alike will utilize DHCP to assigned IP addresses to your ABDs as needed. However, if no DHCP is available, or you wish to specify your IPs/VLANs, that can be set in the Alike Manager, under Tools->Manage ABDs. Then select Add/Edit IPs in the proper system’s sub menu.


Managing Alike ABDs

When selecting an IP/VLAN (XenNetwork) for your ABD(s), please make sure that:

  • The IP(s) are able to access your Alike Server’s ADS CIFS Share
  • Your Alike server must be able to connect (route) to the IP address(es) given to your ABDs
  • The proper XenNetwork (VLAN) has been assigned in the Alike ABD Manager for the intended IP Addresses. Please note: this XenNetwork must be available to all hosts in the pool

The most common error when assigning XenNetworks to your ABDs is the following:

  • “ABD not ready. Failed to connect to after 300 seconds”
  • The means that either your ABD was assigned an IP that cannot route out of its VLAN, or that the Alike Server cannot connect to to the address/network in question.
  • In both cases selecting a different XenNetwork for your ABDs should resolve the issue.

Due to the requirement that all hosts in a pool must be able to see the XenNetwork, in some situations XenNetworks backed by Bonded NICs have been known to cause the error:

  • “ABD not ready. Server cannot attach network (in the case of NIC bonding, this may be because attaching the network on this server would require other networks [that are currently active] to be taken down).”
  • This generally happens when not all hosts in the Xen pool have the NIC bonding configured identically.
  • In these cases, the simplest solution is to select a different XenNetwork that does not have NIC Bonding enabled.
  • If that is not possible, use the settings in the image below under Tools->Settings->System Settings->Advanced in the Alike UI.


Please note: The settings in the image above might side step the host with the underlying problems. If you are still having issues, please open a support ticket.

Final Notes

Once you have configured your ABD networking, it is a good idea to run an ABD Diagnostic Job afterwards. This will test the ABD settings, and help you troubleshoot any connectivity errors.

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