What is NAA, MPX and vml?

The host uses the SCSI INQUIRY command to query a storage device attached to the ESX server and is uses the resulting data to generate a unique identifier. By this mean each attached storage has a unique identified that was generated either by the ESX Server or Storage Device. Device identifiers are unique across all hosts, persistent(will not change even after reboot), and these can be one of the following.

The following are definitions for some of identifiers and their conventions:
  • naa.: or eui.:

    NAA stands for Network Addressing Authority identifier. EUI stands for Extended Unique Identifier. The number is guaranteed to be unique to that LUN. The NAA or EUI identifier is the preferred method of identifying LUNs and the number is generated by the storage device. Since the NAA or EUI is unique to the LUN, if the LUN is presented the same way across all ESXi hosts, the NAA or EUI identifier remains the same. For more information on these standards, see the SPC-3 documentation from the InterNational Committee for Information Technology Standards (T10).
    The represents the partition number on the LUN or Disk. If the is specified as 0, it identifies the entire disk instead of only one partition. This identifier is generally used for operations with utilities such as vmkfstools.

    Example: naa.6090a038f0cd4e5bdaa8248e6856d4fe:3 = Partition 3 of LUN naa.6090a038f0cd4e5bdaa8248e6856d4fe.

  • mpx.vmhba:C:T:L or mpx.vmhba:C:T:L:

    Some devices do not provide the NAA number described above. In these circumstances, an MPX Identifier is generated by ESXi to represent the LUN or disk. The identifier takes the form similar to that of the canonical name of previous versions of ESXi with the mpx. prefix. This identifier can be used in the exact same way as the NAA Identifier described above.
  • vml. or vml.:

    The VML Identifier can be used interchangeably with the NAA Identifier and the MPX Identifier. Appending : works in the same way described above. This identifier is generally used for operations with utilities such as vmkfstools.

    To find out the vml ID you can use the command:

    vmkfstools -q .vmdk

  • vmhba:C:T:L
    This identifier is now used exclusively to identify a path to the LUN. When ESXi detects that paths associated to one LUN, each path is assigned this Path Identifier. The LUN also inherits the same name as the first path, but it is now used an a Runtime Name, and not used as readily as the above mentioned identifiers as it may be different depending on the host you are using. This identifier is generally used for operations with utilities such as vmkfstools.

    Example: vmhba1:C0:T0:L0 = Adapter 1, Channel 0, Target 0, and LUN 0.

    Note: Generally, multi-port fiber channel adapters are equipped with dedicated controllers for each connection, and therefore each controller is represented by different vmhba#. If the adapter supports multiple connections to the same controller, it is represented by a different channel number. This representation is directly dependant on the capability of the adapter.

  • The
    is a unique number assigned to a VMFS volume upon the creation of the volume. It may be included in syntax where you need to specify the full path of specific files on a datastore.

One Response

  1. Karoo..Karoo..Jalsa..
    Karoo..Karoo..Jalsa.. at |

    Thanks for sharing great Info….Keep doing.
    Great Job


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