Hyper-V Agent 9.40

Release Notes, January 22, 2026

1 Overview

The Hyper-V Agent backs up and restores virtual machines (VMs) in Microsoft Hyper-V clusters, Hyper-V standalone hosts, and Microsoft Azure Stack HCI clusters.

The Hyper-V Agent includes two components: the Management service and the Host service. After installing the Hyper-V Agent Management service, you must provide the Hyper-V environment network address and credentials in Portal before you can install Hyper-V Agent Host services.

1.1  Compatibility

Hyper-V Agent services	The Hyper-Agent Management service and Host services in an environment must be the same version. The Hyper-V Agent 9.40 Management service and Host service are not compatible with services from previous Hyper-V Agent versions.
Portal	This Hyper-V Agent version is supported with Portal version 9.31 or later. Important: This Agent version checks the public key of the Portal AMP Proxy certificate when it tries to connect to Portal. If users are hosting their own Portal, we recommend updating the Portal AMP Proxy certificate before new agents are registered to Portal or existing Hyper-V agents are upgraded from version 9.00 or earlier. For more information, see the Portal Installation and Configuration Guide. Note: You cannot manage the Hyper-V Agent with the legacy Windows CentralControl interface.
Vault	This Hyper-V Agent version is supported with Vault version 8.73, 8.72 and 8.70.
Restores from previous Agent versions	This Hyper-V Agent version can restore VMs from backups created using Hyper-V Agent version 9.1x, 9.00, 8.8x, 8.60, 7.4x or 7.30.
Hyper-V versions and VM generations	You cannot restore VMs that were backed up in a newer Hyper-V environment to an older Hyper-V environment. For example, you cannot restore VMs that were backed up in a Windows Server 2019 environment to a Windows Server 2016 environment.

1.2  Release History

Version 9.40.1009, January 22, 2026

1.3  Supported Platforms

The Hyper-V Agent Management service is supported on the following platforms:

• Windows Server 2022 ¹

• Windows Server 2022 Core ¹

• Windows Server 2019

• Windows Server 2019 Core

• Windows Server 2016

• Windows Server 2016 Core

1 The Hyper-V Agent Management service is not yet supported on Windows Server 2022 configured with secured-core security. Note: To restore files and folders from Windows VMs, the Hyper-V Agent Management service must be installed on the same Windows version or a later version than is installed on the Windows VMs. For example, to restore files and folders from Windows Server 2019 VMs, the Hyper-V Agent Management service must be installed on Windows Server 2019 or later.

The Hyper-V Agent Host service is supported on the following platforms:

• Azure Stack HCI 22H2 ²

• Windows Server 2022 ²

• Windows Server 2022 Core ²

• Windows Server 2019

• Windows Server 2019 Core

• Windows Server 2016

• Windows Server 2016 Core

2 The Hyper-V Agent Host service is not yet supported on Windows Server 2022 or Azure Stack HCI configured with secured-core security.

1.4  Supported Guest Operating Systems

Hyper-V Agent 9.40 backs up and restores VMs with Windows and Linux operating systems.

For requirements for application-consistent backups and restores, see Supported VMs and Applications for Application-consistent Backups.

1.5  Supported Storage and Disk Formats

The Hyper-V Agent can back up VMs on:

• Shared Storage (Cluster Shared Volumes)

• Local Storage ³

• SMB3 shares ⁴

The Hyper-V Agent can back up VMs with:

• Virtual disks in VHDX format

• Fixed and dynamically-expanding disks

• Mixed storage (i.e., virtual disks on both local and CSV storage)

The Hyper-V Agent does not back up VMs with pass-through disks or shared virtual disks. See Limitations.

3 In Azure Stack HCI clusters, Hyper-V Agent 9.40 can back up VMs on local or CSV storage but can only restore VMs to CSV storage. See Limitations in Azure Stack HCI Clusters. 4 Hyper-V Agent 9.40 can back up VMs on SMB3 shares but cannot restore VMs to SMB3 shares. However, you can restore VMs to local or CSV storage and then migrate them to SMB3 shares using Hyper-V or another copy method. VMs that are backed up on SMB3 shares cannot be restored using Rapid VM Restore, and specific files and folders cannot be restored from the VMs.

1.6  Supported VMs and Applications for Application-consistent Backups

Hyper-V Agent 9.40 can create application-consistent backups of VMs that meet the following requirements:

• Hyper-V host operating system: Azure Stack HCI, Windows Server 2022, Windows Server 2019 or Windows Server 2016

• VM guest operating system: Windows Server 2022, Windows Server 2019 or Windows Server 2016

• VM configuration version 6.2 or later. To determine the VM configuration version of each VM, open PowerShell on the Hyper-V host and run the following command: Get-VM

• Backup (volume shadow copy) integration service enabled. This service can be selected on the Integration Services pane of a VM’s Settings dialog box.

• No Windows dynamic disks.

On Windows VMs that meet the requirements listed above, the Hyper-V Agent can perform application-consistent backups of the following Microsoft applications:

• SQL Server 2019, 2017, 2016, 2014

• SharePoint Server 2019 and 2016

• Exchange Server 2019 and 2016

• Active Directory 2019 and 2016

As part of an application-consistent backup, the Hyper-V Agent can truncate SQL Server, Exchange and SQL transaction logs for SharePoint Server.

Note: The Agent can truncate logs for default SQL Server instances, but not for named SQL Server instances.

2 NEW FEATURES

Security enhancements

Security enhancements have been added in this Hyper-V Agent version.

3 INSTALLATION NOTES

3.1  Installation Best Practices

For complete installation best practice information, see the Hyper-V Agent User Guide.

For a Hyper-V or Azure Stack HCI cluster, we recommend installing the Management service on a VM in the cluster and configuring the VM for high availability, and installing the Host service on each host in the cluster. The VM where the Management service is installed must resolve to the same DNS server used by the Hyper-V cluster.

For a standalone Hyper-V server, we recommend installing the Management service on a separate Windows server with local network access to the standalone host, and installing the Host service on the standalone host.

3.2  Installation Requirements

Install the Hyper-V Agent Management service on a system that has at least:

• Four CPUs.

• 8 GB of RAM.

• 200 GB of free disk space. This ensures that there is sufficient space for the service and for files generated during backups.

Install the Hyper-V Agent Host service on a host that has at least:

• the minimum Hyper-V system requirements stated by Microsoft.

• 200 GB of free disk space. This ensures that there is sufficient space for the service and for files generated during backups.

The Management service must connect to each host in the Hyper-V environment on a LAN, not a WAN.

The Management service cannot be installed directly on a Hyper-V host in a Hyper-V cluster. You can install the Management service on a standalone Hyper-V host, however.

The Host service cannot be installed on a host where the Windows Agent is installed.

Note: The startup type for Hyper-V Agent services is Automatic (Delayed Start). The delayed service start allows the Agent to clean up files from VMs running using Rapid VM Restore if an Agent host restarts.

3.3  Rapid VM Restore Requirements

To perform a Rapid VM Restore in a Hyper-V cluster:

• The Hyper-V Agent Management server must be joined to the same domain as the cluster.

• The vault must be installed locally (i.e., not on a cloud server or in a remote datacenter).

• The Rapid VM Restore feature must be enabled on the vault. This feature is enabled by default on Satellite vaults. If you have a local Base vault, you can enable the Rapid VM Restore feature by running a script. See Enable the Rapid VM Restore feature on a vault.

If these requirements are not met, Rapid VM Restore does not appear as a restore option in Portal.

3.4  Licensing Requirements

The Hyper-V Agent is only licensed on a vault capacity basis. Agent-based software licensing is not available for the Hyper-V Agent.

3.5  Install/Upgrade

3.5.1  Install

The Management service installation kit name is: Hyper-V Agent Management-9-40-1009.exe

The Host service installation kit name is: Hyper-V Agent Host-9-40-1009.exe

IMPORTANT: After installing the Hyper-V Agent Management service, you must provide the Hyper-V environment network address and credentials in Portal before you can install Hyper-V Agent Host services.

For detailed installation information, see the Hyper-V Agent User Guide.

3.5.2  Upgrade

You can upgrade the Hyper-V Agent to version 9.40 from:

• Version 9.1x

• Version 9.00

• Version 8.84

To upgrade the Hyper-V Agent from a pre-8.84 version, first upgrade to Hyper-V Agent version 8.84, and then upgrade to version 9.40.

You must upgrade the Management service first and then upgrade all Host services in a Hyper-V environment. All Hyper-V Agent services in an environment must be the same version. Hyper-V Agent 9.40 services are not compatible with services from previous Hyper-V Agent versions.

Backups will reseed in some cases after you upgrade a Hyper-V Agent from version 9.00 or earlier to version 9.40:

• Backups will reseed for VMs with dynamically-expanding disks. Data will not be deduplicated on the vault after the reseed, and data from the previous Hyper-V Agent version will not be removed from the vault until specified by the retention settings. For example, if you use Hyper-V Agent 9.00 to back up a VM with dynamically-expanding disks and the resulting safeset is 25 GB in size, then upgrade the Hyper-V Agent to version 9.40 and back up the same VM (with no data changes) again, the next safeset will also be 25 GB in size and the pool size will increase to 50 GB.

• Backups will partially reseed for VMs with fixed disks and user checkpoints.

• Backups will not reseed for VMs with fixed disks and no user checkpoints.

The Management service cannot be installed directly on a Hyper-V host in a Hyper-V cluster. Instead of upgrading a Management service that is installed directly on a Hyper-V host, install the Management service on a separate VM or server and recover jobs and settings from the original Hyper-V Agent.

4 LIMITATIONS, FIXES, and KNOWN ISSUES

4.1  Limitations

This Hyper-V Agent version does not back up:

• VM checkpoints (snapshots)

• VMs that have:

  • Virtual disks in VHD format. Convert virtual disks in VHD format to VHDX format.

  • Pass-through disks

  • Shared VHDXs

This Hyper-V Agent version does not restore:

• VMs that were backed up in a newer Hyper-V environment to an older Hyper-V environment. For example, you cannot restore VMs that were backed up in a Windows Server 2019 environment to a Windows Server 2016 environment.

• More than 50 VMs at a time.

• VMs to SMB3 shares. However, you can restore VMs to local or CSV storage and then migrate them to SMB3 shares using Hyper-V or another copy method. VMs that are backed up on SMB3 shares cannot be restored using Rapid VM Restore, and specific files and folders cannot be restored from the VMs.

• VMs to system partitions.

• Specific files and folders from protected VMs with:

  • Linux guest operating system

  • Volumes on Windows Storage Spaces

  • Windows dynamic disks

This Hyper-V Agent version does not support:

• Email notifications that are configured centrally in Portal. Email notifications for Hyper-V backups must be configured separately for each Hyper-V environment.

• Deferring in scheduled jobs. Deferring is only available for running jobs manually (ad hoc).

• Safeset image (SSI) files.

4.1.1  Limitations in Azure Stack HCI Clusters

In Azure Stack HCI clusters, this Hyper-V Agent version only restores VMs to CSV storage. It does not restore VMs to local storage.

Features that are currently supported in Hyper-V environments are supported in Azure Stack HCI clusters. New features (such as the Azure Kubernetes Service, Azure Disaster Recovery, Storage Replica, Software Defined Networking (SDN) and Secured-core server) are not supported.

The Hyper-V Agent is not supported with standalone servers where the Azure Stack HCI operating system is installed; it is only supported with Azure Stack HCI clusters.

4.2  Best Practices

For best performance in a failover cluster, enable the CSV cache.

4.3  Fixes

• Hyper-V Agents can now register to Portal instances where the AMP Proxy certificate is signed using a stronger algorithm than SHA-256. (5083812)

• When an agent initially cannot connect to a vault because of a network problem, an information message now appears in the log. An error message only appears in the log if the agent cannot connect to the vault on subsequent attempts and the job fails. (2499708, EV-90818, EV-88817, EV-82095)

4.4  Known Issues

4.4.1  Installation and Configuration Issues

• When a Hyper-V Agent is protecting an Azure Stack HCI cluster, "Hyper-V" appears as the operating system for the cluster on the Computers page. "Microsoft Azure Stack HCI" correctly appears as the operating system for each host on the Hosts tab. (EV-86533)

• When upgrading a Host service from version 8.80 to version 9.40, 9.12 or 9.10, the following message might appear on the Management service: Ignored a notification from "hostName" because the sender version 8.132 is not supported. These messages will only appear until all Host services are upgraded to 8.84 or later, and then will no longer appear. (EV-48428)

• If an upgrade does not succeed and the agent rolls back to the previous version, the Management and Host services might not restart automatically.
  WORKAROUND: After a failed upgrade, check whether the Management and Host services are running. If the services are not running, restart them manually. (EV-85317)

• If you install the Management service to a directory that contains non-English characters, the Management service cannot start. (27409)

• If you try to install the Host service to a directory that contains non-English characters, the installation fails. (27234)

• If you remove an email address from the Notifications tab, the Agent continues to send emails to that email address for backups and restores.
  WORKAROUND: Stop and restart the Management service when backups are not running. (27235)

• The Address column on the Hosts tab does not display all IP addresses for a host. The IP address that appears might not be the IP address that you normally use to connect to the host. (27189)

4.4.2  Backup Issues

• If you try to edit a Hyper-V job where credentials are entered for specific VMs in the job, but one of the VMs is no longer available in the Hyper-V environment, an "Oops! Server Error" message appears in Portal. This can occur if a VM has been deleted from the Hyper-V environment, if a Hyper-V host goes down, or VMs are temporarily unavailable.
  WORKAROUND: Delete the Hyper-V job and add the remaining VMs to a new job. To prevent this issue if you plan to delete VMs from a Hyper-V environment, remove the VMs from the Hyper-V backup job before deleting them from the Hyper-V environment. (EV-84450)

• If a VM has a virtual disk saved at the root of a clustered shared volume (CSV), backups may fail for the VM.
  WORKAROUND: Move the virtual disk (VHDX) file to a folder on the CSV. Backups will then succeed. (EV-47961)

• The Agent cannot create an application-consistent backup of a VM if the VM’s name includes one or more square brackets: [ ]. Backups for the VM will be crash-consistent. (EV-47480)

• When performing an application-consistent backup with log truncation of a non-English SQL Server, the Agent might not be able to determine whether the logs were truncated. A warning message appears in the backup log, even though the logs might have been truncated.

• If a job is seeded to a vault using Agent version 7.34 or earlier and reseeded using Agent version 7.50 or later, the vault storage size for the job data cannot be reduced. (EV-25740)

• A Linux VM backup can fail with the following message: A VSS writer has rejected an event with error 0x800423f4. The writer experienced a non-transient error. If the backup is retried, the error is likely to reoccur.
  WORKAROUND: Install the hyperv-daemons package on the Linux VM and try the backup again. (EV-6012)

4.4.3  Restore Issues

• Canceling a Rapid VM Restore can take a long time if the protected VM has a large user-created snapshot. For best performance, we recommend removing snapshots or checkpoints from VMs that will be backed up. (EV-65214)

• If you try to restore a VM to a Hyper-V host with dissimilar hardware (e.g., a different processor) using Rapid VM Restore, the restore sometimes fails from a safeset created using Hyper-V Agent 9.0 or earlier.
  WORKAROUND: Restore the VM using the regular restore method (i.e., not Rapid VM Restore). (EV-66292)

• If you restore the same VM more than once concurrently using Rapid VM Restore and view the Process Details dialog box in Portal, it is difficult to tell which process is for which restore. The Process Details dialog box shows the name of the protected VM but not the restored VM name.
  WORKAROUND: When you restore a VM using Rapid VM Restore, note the Process ID for the restore. (EV-60627)

• After a Rapid VM Restore is canceled, some files are not removed from the ...\Hyper-V Agent Management\Data\Jobs folder. (EV-60026)

• If you restore a VM using Rapid VM Restore, migrate the VM to another host and storage using Hyper-V Manager, and then cancel the Rapid VM Restore, VM snapshots are not removed from the temporary storage location. You must remove the files manually.
  WORKAROUND: Use Portal to migrate a VM restored using Rapid VM Restore to permanent storage. (EV-59864)

• A Rapid VM Restore does not succeed if the Management service is installed on a machine that does not have a C drive, has insufficient free space on the C drive, or has security policies that limit access to the C: drive. For assistance with this issue, please contact Support. (EV-59940)

• If the network connection to the vault is interrupted during a restore, the restore might fail with the following warning message in the restore log: invalid crc detected in sidf data (EV-48450)

• If a protected VM includes a fixed-size disk with many zero-filled blocks, restoring the VM can take much longer than backing up the VM. (EV-47190)

• When you try to recover jobs and settings from an offline Agent in a Hyper-V environment with many virtual machines, Portal could time out so that the recovery cannot be completed.
  WORKAROUND: A configuration change in Portal can allow the Hyper-V Agent recovery to succeed. For more information, please contact Support. (EV-47193, EV-47032)

• During a file and folder restore from a seed backup, a shared volume might be labeled as “Unknown” instead of with its original drive letter. (EV-47932)

• During a file and folder restore, when you try to access a virtual disk that was mounted in an NTFS folder on a protected VM, you cannot access the virtual disk contents from the folder where it was mounted. Instead, the mounted disk appears as a separate disk named “Unknown” in the share. (EV-46075)

• During a file and folder restore, if you map the UNC share path to a drive letter, an “Access is Denied” error appears when you try to access the drive from a command prompt.
  WORKAROUND: Use a PowerShell command prompt to access the mapped drive. (EV-45028)

• If you try to restore a VM with a network adapter and a snapshot to a host that does not have a network adapter with the same name, the restore fails. However, the VM’s disks are restored.
  WORKAROUND: Do one of the following:

  • After restoring the VM, manually create a VM and attach the restored disks. Manually delete the snapshot and then associate the VM with a new network adapter.

  • Restore the VM without selecting the Enable network connectivity check box.

  Note: Consistent with Microsoft best practices, we recommend not taking user-level snapshots of VMs that will be backed up in a production environment. (EV-8491)

• If you terminate a restore, and one or more VMs are not completely restored, partial VM files will remain on disk and must be cleaned up manually. (25962)

  5 PRODUCT SUPPORT

  5.1  Technical Support

  Contact information for your provider is available through the Need Help button in Portal.

  5.2  Product Updates

  Product updates are available through your provider.

  5.3  Documentation

  The following documentation is available for this product:

  • Server Backup online help

  • Release notes (this document)

  • User Guide