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arcserve-KB : Arcserve UDP Agentless: Can the Host-Based VM Backup Plan Proxy be located on a VM?

Last Update: 2016-11-23 12:52:21 UTC

When you set up an arcserve UDP Agentless Host-Based VM Backup Plan you must define a host to act as the 'host-based backup proxy' server. It is generally considered a best practice to locate the proxy role for UDP Agentless Host-Based VM backup on to a physical server.

The proxy host requires that the UDP Agent (Windows) has been installed. The proxy host may also require VMware VIX API. VIX is not mandatory for UDP backup or restore operations, but if you require certain functions such as pre/post commands, application logs purged for SQL or Exchange server, VIX API is required to be installed on the proxy host.

Can the UDP Host-Based VM Backup Proxy be located on a VM?

Placing the arcserve UDP Agentless Host-Based VM Backup proxy role on a VM is supported however this may introduce problems in the environment due to the transport mode used. When setting up the proxy on a VM the default transport mode used will be 'HOTADD.'  Using hotadd transport mode can overburden the proxy VM host and this may result in problems with post backup cleanup tasks which can lead to snapshot consolidation issues and orphaned snapshots which will require an administrator to perform manual steps to resolve.

The following is an excerpt from the VMware VDDK 5.5.1 Release Notes which explains in more detail:

Cleanup function does not remove the HotAdd disks.
After virtual disks are HotAdded with VixDiskLib_Open, they are not automatically cleaned up (hot-removed) by VixDiskLib_Cleanup. After disk is HotAdded or mounted, if a backup application crashes during backup due to network failure or power outage or any other issue, the leftover HotAdded disk must be cleaned up manually. Starting the backup application after a crash and calling VixDiskLib_Cleanup thereafter will clean up the mount directory, but will not hot-remove the disk. The fix, available in a future release, is to clean up or hot-remove any HotAdd disk based on mount information when VixDiskLib_Cleanup is called.

Due to these concerns it is recommended as a best practice to place the UDP Host-Based VM Backup Proxy role on a physical server. However, if this is not possible and a VM host must be used, the recommendation is to force the proxy host to use NBD Transport Mode.

Network Block Device (NBD) transport mode, also referred to as LAN transport mode, uses the Network File Copy (NFC) protocol to communicate. Various VDDK and VCB operations use one connection for each virtual disk that it accesses on each ESX/ESXi Server host when using NBD.  It should also be noted that when using NBD transport mode, there may be additional resource constraints and increased i/o load on the network. 

It is therefore recommended to consider following Arcserve UDP best practice recommendations which indicate that the arcserve UDP Agentless Host-Based VM Backup Proxy should be installed on a physical host for best performance and results.

More Information:
For information about how to set up a UDP Host-Based BM Backup Plan please refer to the chapter:
How to Create a Host-Based Virtual Machine Backup Plan in the arcserve Unified Data Protection 5.0 Solutions Guide.

For information about how to change the transport mode used by the UDP Host-Based VM Backup Proxy, please refer to the chapter: Define a Transport Mode for Host-Based Agentless Backup and Restore

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