63997: Acronis Cyber Protect: Backup fails with "Windows error: (0x800705B4) This operation returned because the timeout period expired"

    Last update: 18-11-2022


    Activity fails with one of the following errors:

    Windows error: (0x800705B4) This operation returned because the timeout period expired


    Operating system error: This operation returned because the timeout period expired


    1) If the operating system is Windows Server 2012 R2 and Windows Server 2016, the error may be caused by a known Microsoft Windows issue. See Troubleshooting section for details.

    2) The issue is caused by too intensive workload on the machine at the backup start time.

    A VSS writer is application-specific software that acts to ensure that application data is ready for shadow copy creation. Windows OS includes a set of VSS writers and VSS-aware applications install own VSS writers to the machine. If the workload on the machine is high at the backup time, a VSS writer might not respond in the expected timeframe, that is, reach a timeout. A backup made under these conditions might not be restorable, that is why Acronis software cancels this backup and shows this error message.

    Timeout issue of VSS Writers appears when Acronis Agent is waiting for snapshot creation. It is caused by default timeout value for the VSS writers (60 seconds). Since opening and flushing volumes takes significant time, after 60 seconds writers fail and snapshot is aborted, especially if disk load is high.


    Beginning with Acronis Cyber Backup 12.5 Update 4 (build 12730) and Acronis Cyber Protect Cloud 7.9 (build 12960), new performance mechanisms are implemented to the software to improve handling of VSS requests. Please update to the latest available build and check if backup works.

    If update is not possible or did not resolve the issue, follow the troubleshooting steps depending on the operating system you use:

    If the affected system is Windows Server 2012 R2 and Windows Server 2016, verify if the system is affected by a known issue:

    If the system is not Windows Server 2012 R2 and Windows Server 2016 or if above solution is not applicable, increase VSS operations timeout or reschedule the backup to a different time when disk load is lower.

    How to increase timeout for VSS operations

    1. Open Windows Registry EditorStart -> search -> type regedit.exe and press Enter.
    2. Locate the following Key: HKEY_LOCAL_MACHINE\SOFTWARE\Acronis
    3. Inside, locate a key called SnapAPI. If it doesn't exist, create it
    4. Inside SnapAPI key create a DWORD32 value called "VssOperationTimeout"
    5. Set this value to "decimal" and specify "3600" which is the equivalent of 1 hour.

    Alternatively, you can use these Powershell commands:

    New-Item -Path "HKLM:\SOFTWARE\Acronis" -Name SnapAPI
    This may fail if the path already exists, just proceed further.

    New-ItemProperty -Path "HKLM:\SOFTWARE\Acronis\SnapAPI" -Name "VssOperationTimeout" -Value "3600" -PropertyType "DWORD"
    You can change value to fit the snapshot time.

    Run backup during low I/O period

    To determine what time is better for proper handling of VSS snapshot creation requests, we suggest to use the following scheme:

    • Enable Task failure handling option in the affected backup plan and set interval between attempts to 40-50 minutes and number of attempts 20
    • Start backup. It will be running in nonstop mode until snapshot creation is successful
    • Note the time when snapshot is created successfully and schedule backup to this time to avoid further snapshot timeout issues.

    You can also use the Perfmon utility to check current I/O load on disks and find right time for snapshot operations.

    If rescheduling backup to the time of lower I\O load does not help, consider the following options to troubleshoot the issue:

    1) Download VSS Doctor to investigate and troubleshoot issues with VSS on the affected Agent machine

    2) For Windows Server 2008, 2008R2, 2012, 2012R2, 2016 create a snapshot using Diskshadow tool to check the functionality of the VSS service components. If issue occurs on Workstation OS, skip this step.

    If any writer fails with an error or creating a snapshot with Diskshadow does not end with "Number of shadow copies listed: x", you need to troubleshoot this writer and make sure it is functioning correctly before using VSS backup in Acronis Software. Acronis Cyber Backup relies on VSS to perform backup operations and correct functioning of VSS writers is a prerequisite for successful snapshot creation.  

    If suggested steps did not help to localize the issue, collect the following information and contact Acronis Support:

    1. VSS Doctor report
    2.  Result of backup with Diskshadow (as screenshots or output to file)
    3. Acronis System information from the affected Agent machine:

    More information

    Workaround for Acronis Cyber Backup 12.5: create backups with a bootable media. Backups of a shut down system are application-consistent by default. See this article for details. 

    (!) Creating backups from bootable media is not available in Acronis Cyber Protect Cloud.