Dell Unity: How to View and Change a LUN's Host Logical Unit Number (User Correctable)

Summary: How to view and change Host Logical Unit (HLU) ID numbers in Unity.

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Instructions

CAUTION: If you modify a Host Logical Unit (HLU) ID and click OK, a warning message appears. Depending on the operating system, the host may require being put in maintenance mode first. Consult the host operating system vendor for full details.

 

View Host LUN ID

  1. Under Storage, select Block > LUNs.
  2. Double-click the relevant LUN (or select it and click the Edit button).
  3. Go to the Host Access tab. Here the list of hosts mapped to this LUN is seen, and the LUN ID (HLU) for each of these hosts.
    Example:
    Screnshot of hosts mapped to a LUN
    Figure 1: Screenshot of hosts mapped to a LUN

 

Modify Host LUN ID

  1. Verify if the hosts you are modifying must be in maintenance mode (according to your operating system vendor). Put the hosts in maintenance mode if it is required.
  2. Select the relevant hosts and at the top, click on Modify Host LUN IDs.
  3. Click on the pencil icon in the "Host LUN ID" column of the hosts being changed.
  4. Change the HLU ID to the same number across all hosts. (See the "Additional Information" section for more information)

  5. Once all the IDs are the same, click on OK.
    Change the HLU ID to the same number across all hosts
    Figure 2: Change the HLU ID to the same number across all hosts.

    Message asking for confirmation of changes
    Figure 3: Message asking for confirmation of changes

 

Additional Information

  • All hosts within the same cluster connected to a common LUN must have matching Host LUN IDs. The Host LUN IDs must be unique across all LUNs attached to the hosts.
    • Note: There are exceptions, such as backup servers or RecoverPoint (RP).
    • When the LUN is attached to both a cluster and server, and a backup/RP HLU conflicts reporting on the LUN can be ignored.
    • Therefore, any reported HLU conflicts for a backup or RecoverPoint server should be ignored when reviewing HLU conflicts.
  • The first LUN accessed by a Host is automatically assigned LUN ID (HLU) of 0.
  • Changing the Host LUN ID value requires an outage or downtime window.
  • The Modify LUN IDs feature enables you to change the IDs of the LUNs so that you can achieve the same mapping view of LUNs for each host in a cluster. It also enables you to configure a bootable LUN that allows a host to boot from the Storage Area Network (SAN).
  • To configure a bootable LUN, set the value for the relevant LUN to 0.
Having mismatched HLUs may lead to performance issues like:
  • SCSI Reservation conflicts with LUNs
  • Trespass storms
  • Disconnects or loss of access or connectivity issues (due to intense trespassing)
  • Potential data corruption

 

Affected Products

Dell EMC Unity Family

Products

Dell EMC Unity Family
Article Properties
Article Number: 000022538
Article Type: How To
Last Modified: 25 Jan 2024
Version:  4
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