Use vSphere On-disk Metadata Analyser (VOMA) to identify and fix incidents of metadata corruption that affect file systems or underlying logical volumes.


You might need to check metadata consistency of a file system or a logical volume backing the file system when you experience problems with various functionalities on a VMFS datastore or a virtual flash resource. For example you might want to perform a metadata check if one of the following occurs:
  • You experience storage outages.
  • After you rebuild RAID or perform a disk replacement.
  • You see metadata errors in the vmkernel.log file.
  • You are unable to access files on a VMFS.
  • You see corruption being reported for a datastore in events tabs of vCenter Server.


To check metadata consistency, run VOMA from the CLI of an ESXi host. VOMA can be used to check and fix metadata inconsistency issues for a VMFS datastore or a virtual flash resource. To resolve errors reported by VOMA, consult VMware Support.

Follow these guidelines when you use the VOMA tool:
  • Make sure that the VMFS datastore you analyze does not span multiple extents. You can run VOMA only against a single-extent datastore.
  • Power off any virtual machines that are running or migrate them to a different datastore.
The following example demonstrates how to use VOMA to check VMFS metadata consistency.
  1. Obtain the name and partition number of the device that backs the VMFS datastore that you need to check.

    #esxcli storage vmfs extent list

    The Device Name and Partition columns in the output identify the device. For example:
    Volume Name  XXXXXXXX  Device Name                             Partition  
    1TB_VMFS5    XXXXXXXX  naa.600508e000000000b367477b3be3d703    3
  2. Run VOMA to check for VMFS errors.

    Provide the absolute path to the device partition that backs the VMFS datastore, and provide a partition number with the device name. For example:

    # voma -m vmfs -f check -d /vmfs/devices/disks/naa.600508e000000000b367477b3be3d703:3

    The output lists possible errors. For example, the following output indicates that the heartbeat address is invalid.

    Phase 2: Checking VMFS heartbeat region
     ON-DISK ERROR: Invalid HB address
    Phase 3: Checking all file descriptors.
    Phase 4: Checking pathname and connectivity.
    Phase 5: Checking resource reference counts.
    Total Errors Found:           1

Command options that the VOMA tool takes include the following.

Table 1. VOMA Command Options
Command Option Description
-m | --module The module to run:
  • vmfs. This is a default option. You can check VMFS3 and VMFS 5 datastores. If you specify this module, minimal checks are performed for LVM as well.
  • vmfsl. Check file systems that back virtual flash volumes.
  • lvm. Check logical volumes that back VMFS datastores.
-f | --func Functions to be performed:
  • query. List functions supported by module.
  • check. Check for errors.
  • fix. Check and fix errors.
-d | --device Device or disk to be inspected. Make sure to provide the absolute path to the device partition backing the VMFS datastore. For example, /vmfs/devices/disks/naa.00000000000000000000000000:1.
-s | --logfile Specify the log file to output the results.
-v | --version Display the version of VOMA.
-h | --help Display the help message for the VOMA command.