Use VMware Ondisk Metadata Analyser (VOMA) when you experience problems with your VMFS datastore and need to check metadata consistency of VMFS or logical volume backing the VMFS volume.

The following examples show circumstances in which you might need to perform a metadata check:

  • You experience SAN 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 the VMFS datastore that are not in use by any other host.


To check metadata consistency, run VOMA from the CLI of an ESXi host version 5.1 or later. VOMA can check both the logical volume and the VMFS for metadata inconsistencies. You can use VOMA on VMFS3 and VMFS5 datastores. VOMA runs in a read-only mode and serves only to identify problems. VOMA does not fix errors that it detects. Consult VMware Support to resolve errors reported by VOMA.

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.

Follow these steps when you use the VOMA tool 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

The VOMA tool uses the following options.

Table 1. VOMA Command Options

Command Option


-m | --module

The module to run: vmfs or lvm. If you specify vmfs, minimal checks are performed for LVM as well. The default module is vmfs.

-f | --func

Functions to be performed:

query - list functions supported by module.

check - check for 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.