VMFS Datastores Are Inaccessible

Posted: May 19, 2011 in VMware

Problem : One of the LUN becomes inaccessible as it came up as snapshot LUN .

You can check if one LUN is seen from ESX as snapshot LUN by logging into ESX and do the following .

[root@uesx05 /]# cd /var/log
[root@uesx05 log]# less vmkernel | grep UQNAP:LUN14
May 19 12:13:59 uesx05 vmkernel: 3:21:24:42.383 cpu6:4110)Vol3: 1010: [label: UQNAP:LUN14, uuid: 4dcc9251-36dbd158-1405-001b24a2e4d4] detected as a snapshot file system.

As you can see that UQNAP:LUN14 has been detected as Snapshot file system .Also you can check more on this status as

By connecting directly to the ESX host service console:

  1. Log in as root to the ESX host which cannot mount the datastore using an SSH client. For more information, see

    Run the command:

    esxcfg-volume -l

    The results appear similar to:

    VMFS3 UUID/label: 4b057ec3-6bd10428-b37c-005056ab552a/ UQNAP:LUN14
    Can mount: Yes
    Can resignature: Yes
    Extent name: naa.6000eb391530aa26000000000000130c:1 range: 0 – 1791 (MB)

    Record the UUID portion of the output. In the above example the UUID is 4b057ec3-6bd10428-b37c-005056ab552a.

Solution :

To mount it back again ew need to resignature that LUN and mount it back again .

1. Log in as root to the ESX hos

2. esxcfg-volumn -r  “uqnap:lun14”

3. esxcfg-rescan vmhba32

4. Then complete rescan HBA of all esx.

5. Then you will see this LUN is mounted as a snapLUN .

6. Unregister all VM resides from old LUN ( after that you can see that LUN will disappear)

7. Rename the new snap LUN as old one ( UQNAP:LUN14)

8. Register back all VM again and power on .

  1. Mohamamd says:

    With esxcfg-volumn -r , you are basically resignaturing the LUN and the ID has been changed . Thats why you need to reregister all the VM .

    If you want to keep the existing signature and dont want to unregister and register back all the VM again do the following instead .

    [root@desx03 ~]# esxcfg-volume -l
    VMFS3 UUID/label: 4d40f33e-225eddec-7ac3-001b245ec143/DQNAP01:LUN07
    Can mount: Yes
    Can resignature: Yes
    Extent name: naa.600140548c9c965d6b05d49c9daeccda:1 range: 0 – 2096895 (MB)

    [root@desx03 ~]# esxcfg-volume -M “4d40f33e-225eddec-7ac3-001b245ec143”
    Persistently mounting volume 4d40f33e-225eddec-7ac3-001b245ec143

    [root@desx03 ~]# vmkfstools -V ( To Refresh the datastore )

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