Datastore is missing after SAN power failure but LUN is presented and visible on ESX.

Datastore is missing after SAN power failure but LUN is presented and visible on ESX.

Article Summary:

This article provides information on how to troubleshoot when a Datastore is missing after SAN power failure but LUN is presented and visible on ESX..


  • VMware vSphere 5.x


  • A power failure on the SAN causes one datastore to no longer be visible on all ESX hosts.
  • Prior to the outage, the LUN was presented and visible to all ESX hosts.


To resolve this issue:

  1. To identify the devices presented to the ESX Server, run the command:

    esxcfg-vmhbadevs -q

  2. To identify datastores and the associated devices, run the command:

    esxcfg-vmhbadevs -m

    For the datastore that is missing, you see a message similar to:

    cannot open volume /vmfs/volumes/4569-08764-eb45-2347a/

  3. Compare the list from the output of step 1 with the output of step 2 to identify the device which is missing.

    For example, if you see /dev/sdl in the output of step 1, but it does not appear in the output of step 2, /dev/sdl is the missing device.

  4. To verify the disk is set to VMFS, run the command:

    fdisk -lu device

    For example:

    fdisk -lu /dev/sdl

  5. If this is correct, verify that the magic number is correct by running the command:

    hexdump -c /dev/sdl

  6. After verifying that it is correct, run a rescan by running the command:

    esxcfg-rescan vmhbaX

    Where X is the appropriate number in your environment.

  7. Check the /var/log/vmkernel log for a Failed to reserve volume error. If the error exists, perform a LUN reset.

    For example:

    vmkfstools -L lunreset /vmfs/devices/disks/vmhba1\:1\:0\:0

  8. Check the /var/log/vmkernel log to verify that the LUN reset succeeded by searching for the device reset message.

  9. Mount the datastore by running the command:

    vmkfstools -V


  • If the datastore still does not mount, this indicates that there is a lock on the Storage Processor, as none of the ESX hosts have the datastore presented. Since the lock will not be from another ESX host at this point, try trespassing the LUN from one storage processor to another, and then rescan the HBA on the host. The datastore mounts successfully after the rescan.

  • These steps are only valid if one device is missing after an event.

Reference: Datastore missing after SAN power failure but LUN is presented and visible on ESX (1026439)

Quick Tips content is self-published by the Dell Support Professionals who resolve issues daily. In order to achieve a speedy publication, Quick Tips may represent only partial solutions or work-arounds that are still in development or pending further proof of successfully resolving an issue. As such Quick Tips have not been reviewed, validated or approved by Dell and should be used with appropriate caution. Dell shall not be liable for any loss, including but not limited to loss of data, loss of profit or loss of revenue, which customers may incur by following any procedure or advice set out in the Quick Tips.

Identificación del artículo: SLN288151

Última fecha de modificación: 11/08/2013 12:00 AM

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