36993: Acronis Backup: Corrupted MFT, Run List, Block Bitmap or Index Causes Backup in Sector-by-Sector Mode

Corrupted MFT, Run List, Block Bitmap or Index causes backup in Sector-by-Sector Mode. The workaround is to disable "Shadow Copy Optimization Writer".

Symptoms

  1. A backup task has been defined including Windows Server 2008 R2 or Windows SBS 2011 as virtual guest systems.
  2. The backup task runs.
  3. After the backup, you find in logs information that the backup switched to sector-by-sector mode. This sector-by-sector mode is slower than the default method.

    The messages in the logs look similar to these:

    Error code: 46
    Module: 7
    LineInfo: a5695862aaf8e75e
    Fields: PartitionId : 219
    Message: Forced sector-by-sector mode.
    --------------------
    Error code: 28
    Module: 7
    LineInfo: 89d94b01b483dcca
    Fields:
    Message: Run list is corrupted.

    OR

    --------------------
    Error code: 46
    Module: 7
    LineInfo: a5695862aaf8e75e
    Fields: PartitionId : 227
    Message: Forced sector-by-sector mode.
    --------------------
    Error code: 22
    Module: 7
    LineInfo: 89d94b01b483dcdb
    Fields:
    Message: Block bitmap is corrupted.

    OR

    --------------------
    Error code: 46
    Module: 7
    LineInfo: a5695862aaf8e75e
    Fields: PartitionId : 997
    Message: Forced sector-by-sector mode.
    --------------------
    Error code: 37
    Module: 7
    LineInfo: 89d94b01b483de5a
    Fields:
    Message: Index is corrupted


    OR

    --------------------
    Error code: 46
    Module: 7
    LineInfo: a5695862aaf8e75e
    Fields: PartitionId : 845
    Message: Forced sector-by-sector mode.
    --------------------
    Error code: 24
    Module: 7
    LineInfo: ef8b1618a4c0dd9c
    Fields:
    Message: MFT bitmap is corrupted.

    OR

    Event code: 46
    Module: 7
    LineInfo: a5695862aaf8e7b0
    Fields:
    Message: Forced sector-by-sector mode.
    --------------------
    Event code: 11
    Module: 7
    LineInfo: 6b426cba4c49b72b
    Fields:
    Message: FAT is corrupted.

Solution

These solutions can be applied to all the issues described below and we recommend to use them before any further step.

  • Check all the filesystems inside the guest OS with chkdsk, see solution #1 "Run list is corrupted" for more details.
    • (!) Please keep in mind that some filesystems like SystemReserved or RECOVERY can be hidden and one has to assign a disk letter to such a partition to make it accessible for chkdsk.
  • Reinstall VMWare Tools or Hyper-V Integration Services inside the guest OS and reboot the system.

If these steps don't resolve the issue, proceed with the following solutions.

1. Run list is corrupted

Cause:

First of all there may be a problem with the file system inconsistency inside the backed up VM, so the Acronis product is unable to properly read from it and therefore starts backing up the machine in sector-by-sector mode.

Solution:

To resolve this you should perform file system check via embedded Windows utilities. Please run CHKDSK utility on all the logical volumes inside the virtual machine:

  • Go to the Command Prompt (Start -> Run -> cmd);
  • Enter the command: chkdsk DISK: /r
    (where DISK is the drive letter of the partition you need to check.) 
    (!) Checking the C: drive may require you to reboot the machine, so if reboot is not possible at the moment run chkdsk without "/r" parameter. If no problems are revealed then you won't need to run "chkdsk /r" - in this case check the below sections for possible workaround.

2. Block bitmap is corrupted

Cause:

These messages may appear if Acronis vmProtect cannot recognize the virtual disk block structure of the virtual machine due to the specifics of the blocks size.

Solution:

Turn off the virtual machine and extend the virtual disk size (from vSphere client) by any value, for example, by 10 MB. This action will rebuild the virtual disk structure and fix the potential block size problem. If this does not help please try the next solution.

3. Index is corrupted and MFT bitmap is corrupted

Cause:

These messages may appear in rare cases when the virtual machine is under high load during the backup. In these cases there may be a situation when there is data recorded in NTFS journal which is not yet flushed to the volume - the file system therefore is recognized as corrupt since Acronis products are unable to read the NTFS journal properly and require that the data is flushed to disk in order to read from it. This situation forces the sector-by-sector backup mode.

The same issue is applicable to Acronis vmProtect 7, but in this version the message about switching to sector-by-sector mode was hidden and was available in debug mode only. This issue does not happen each time and depends on the particular VM system state at the snapshot time.

This is planned to be fixed future versions of Acronis vmProtect and Acronis Backup & Recovery Virtual Edition.

Workaround:

The problem is caused by specific VSS writer which is installed by default in Windows 2008 R2. The writer is called "Shadow Copy Optimization Writer" (http://msdn.microsoft.com/en-us/library/bb968827%28VS.85%29.aspx#shadow_...). It performs VSS snapshot modifications which are causing the issue described above and therefore the solution is to disable this VSS writer from processing by VMware tools. Please check the following VMware article on how to disable specific VSS writers:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd...

In short you should create vmbackup.conf %ALLUSERSPROFILE%\Application Data\VMware\VMware Tools\ on the Windows 2008 R2/SBS 2011 VM which is being backed up, open this file in Notepad editor and add the following stroke:

Shadow Copy Optimization Writer

After that restart VMware Tools Service and try to back up this VM once again.

The above described method is in fact a workaround and until the normal fix is available you should either use this method or ignore these messages. If you ignore this issue please note that in some cases files/folders recovery from such backups may not be possible, however it will still work in most cases even despite this message (it is a random behavior). You can still recover the entire VM from these backups or run it from backup (the Run VM from Backup feature) for granular recovery purposes. See also Acronis vmProtect 8: Run VM from Backup.

 

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