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Veeam Backup & Replication Help Center  > User Guide >  Overview > Backup > Backup of VMs on Local Storage and CSV > Backup Modes > Offhost Backup

Offhost Backup

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In the offhost backup mode, backup processing is shifted from the source Hyper-V host to a dedicated machine – an offhost backup proxy. The offhost backup proxy acts as a “data mover”– the Veeam transport service running on it retrieves VM data from the source datastore, processes it and transfers to the destination. This type of backup does not impose load on the Hyper-V host — while resource intensive backup operations are performed on the offhost backup proxy, production hosts remain unaffected. To learn more, see Offhost Backup Proxy.

To perform offhost backup, Veeam Backup & Replication uses transportable shadow copies. The transportable shadow copy technology enables you to create a snapshot of a data volume on one server and import, or mount, it onto another server within the same subsystem (SAN) for backup and other purposes. The transport process is accomplished in a few minutes, regardless of the amount of the data. The process is performed at the SAN storage layer so it does not impact the host CPU usage or network performance.  To learn more, see

To be able to perform offhost backup, you must meet the following requirements:

1.You must configure an offhost backup proxy. The role of an offhost backup proxy can be assigned only to a Microsoft Windows 2008 Server R2 machine with the Hyper-V role enabled, to a Microsoft Windows Server 2012 machine with the Hyper-V role enabled or to a Microsoft Windows Server 2012 R2 machine with the Hyper-V role enabled.

Note that the version of the Hyper-V host and offhost backup proxy should coincide. For example, if you use a Microsoft Windows 2008 Server R2 machine with the Hyper-V role enabled as a Hyper-V host, you should deploy the offhost backup proxy on a Microsoft Windows 2008 Server R2 machine with the Hyper-V role enabled.

2.In the properties of a backup or replication job, the offhost backup method must be selected. If necessary, you can point the job to a specific proxy (to learn more, see the Configuring Advanced Options for Offhost Backup Proxies section).

3.The source Hyper-V host and the offhost backup proxy must be connected (through a SAN configuration) to the shared storage.

4.To create and manage volume shadow copies on the shared storage, you must install and properly configure a VSS hardware provider that supports transportable shadow copies on the offhost proxy and Hyper-V host. Typically, when configuring a VSS hardware provider, you need to specify a server controlling the LUN and disk array credentials to provide access to the array.

The VSS hardware provider is usually distributed as a part of client components supplied by the storage vendor. Any VSS hardware provider certified by Microsoft is supported. Note that some storage vendors may require additional software and licensing to be able to work with transportable shadow copies.

5.If you back up VMs whose disks reside on a CSV with Data Deduplication enabled, make sure that you use a Microsoft Windows 2012 R2 machine as an offhost backup proxy and enable the Data Deduplication option on this offhost backup proxy. Otherwise, offhost backup will fail.

The offhost backup process includes the following steps:

1.Veeam Backup & Replication triggers a snapshot of the necessary volume on the production Hyper-V host.

2.The created snapshot is split from the production Hyper-V server and mounted to the offhost backup proxy.

3.The Veeam transport service running on a backup proxy uses the mounted volume snapshot to retrieve VM data; the VM data is processed on the proxy server and copied to the destination.

4.Once the backup process is complete, the snapshot is dismounted from the offhost backup proxy and deleted on the SAN.




If you plan to perform offhost backup for a Hyper-V cluster with CSV, make sure you deploy an offhost backup proxy on a host that is NOT a part of a Hyper-V cluster.
When a volume snapshot is created, this snapshot has the same LUN signature as the original volume. Microsoft Cluster Services do not support LUNs with duplicate signatures and partition layout. For this reason, volume snapshots must be transported to an offhost backup proxy outside the cluster. If the offhost backup proxy is deployed on a node of a Hyper-V cluster, a duplicate LUN signature will be generated, and the cluster will fail during backup or replication.

Helpful resources:

A list of tested VSS hardware providers for DPM:

Links to resources and documentation from some of storage vendors:

HP Support Center:

DELL PowerVault: The VSS hardware provider for Dell PowerVault can be found on the Resource CD.

DELL Equal Logic:, (account required). The VSS hardware provider is a part of Host Integration Tool (HIT/Microsoft)

IBM DS6000 & DS8000 series:

EMC (Clarion and Symmetrix): (account required). Go to Support > Software downloads and licensing > Downloads T-Z > VSS Provider.

To get detailed information, contact your SAN vendor.

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