How are new LUNs discovered by an ESXi Host?

How are new LUNs discovered by an ESXi Host?

A manual rescan operation is required every time a new LUN is added

ESXi hosts automatically detects new LUNs as they are presented

A rescan operation is periodically performed by ESXi hosts to detect any new LUNs

A reboot operation is required to detect newly presented LUNs

iSCSI SAN Configuration Guide, page 26.
The VMkernel discovers LUNs when it boots, and those LUNs are then visible in the vSphere Client. If changes are made to the LUNs, you must rescan to see those changes.
New LUNs created on the iSCSI storage
Changes to LUN access control
Changes in connectivity

4 Comments on “How are new LUNs discovered by an ESXi Host?

  1. Bubez says:

    A wrong
    D correct
    The question ask about the ESXi itself. The only method is a reboot operation.
    Obviously, performing a manual rescan is enough to see the new lun(s), but it’s not the only method: if you like you can reboot the host.

    1. MikeyH says:

      This is a badly worded question.

      D would work, in most situations you never reboot the ESX host.
      A is required if you can’t reboot the host.

      I’d go for A as if you are going to reboot the ESX host it’s not doing it by itself.. you’ve told it to reboot in which case you may as well have rescan’ed it instead.

  2. Bubez says:

    Sorry! A is correct!
    Since all questions should be answered using the official documentation, I was in error. It was my wrong question – interpretation, this is the correct ref.
    Pg. 124 VSphere Storage – ESXi 5.0
    Perform the manual rescan each time you make one of the following changes.
    *Zone a new disk array on a SAN.
    *Create new LUNs on a SAN. (our situation)
    *Change the path masking on a host.
    *Reconnect a cable.
    *Change CHAP settings (iSCSI only).
    *Add or remove discovery or static addresses (iSCSI only).
    *Add a single host to the vCenter Server after you have edited or removed from the vCenter Server a datastore shared by the vCenter Server hosts and the single host.

  3. celembribor says:

    I think C is correct
    When you perform VMFS datastore management operations, such as creating a VMFS datastore or RDM, adding an extent, and increasing or deleting a VMFS datastore, your host or the vCenter Server automatically rescans and updates your storage. You can disable the automatic rescan feature by turning off the Host Rescan Filter. config.vpxd.filter.hostRescanFilter – Host Rescan Filter Note: If you turn off the Host Rescan Filter, your hosts continue to perform a rescan each time you present a new LUN to a host or a cluster.

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