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VMFS Volume Can Be Erroneously Recognized as a Snapshot (6482648)

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Details

In some configurations, a VMFS-3 volume can be recognized as a snapshot even when it is not.
 
Note: This article pertains to ESX 3.x. For information on handling of snapshot LUNs in ESX 4.x, see vSphere handling of LUNs detected as snapshot (1011387).
 
This issue has been tracked to this scenario:
  • Server A is presented LUNs 1, 2, and 3
  • The same LUNs are then presented to server B as LUNs 5, 6, and 7.
  • When a VMFS-3 volume is created on LUNs 1, 2, and 3 via server A, rescanning the SAN from server B results in the latter complaining that volumes on LUNs 5, 6, and 7 are snapshots of those on LUNs 1, 2, and 3.
The vmkernel logs on server B show:

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.787 cpu13:1046)LVM: 5670: Device vmhba1:0:5:1 is a snapshot:

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.787 cpu13:1046)LVM: 5676: disk ID: <type 2, len 22, lun 5, devType 0, scsi 5, h(id) 10179760818951437974>

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.787 cpu13:1046)LVM: 5678: m/d disk ID: <type 2, len 22, lun 1, devType 0, scsi 5, h(id) 10179760818951437974>

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.790 cpu13:1046)LVM: 5670: Device vmhba1:0:6:1 is a snapshot:

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.790 cpu13:1046)LVM: 5676: disk ID: <type 2, len 22, lun 6, devType 0, scsi 5, h(id) 11552037668126695191>

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.790 cpu13:1046)LVM: 5678: m/d disk ID: <type 2, len 22, lun 2, devType 0, scsi 5, h(id) 11552037668126695191>

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.794 cpu13:1046)LVM: 5670: Device vmhba1:0:7:1 is a snapshot:

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.794 cpu13:1046)LVM: 5676: disk ID: <type 2, len 22, lun 7, devType 0, scsi 5, h(id) 13372428508588014685>

Jul 18 10:58:31 ServerB vmkernel: 0:14:17:59.794 cpu13:1046)LVM: 5678: m/d disk ID: <type 2, len 22, lun 3, devType 0, scsi 5, h(id) 13372428508588014685> 
 
If the Storage Processors are not configured as required for use with ESX Server (see corresponding vendor for detailed configuration documents), it can result in this behavior.
 
Sample array misconfiguration that could result in this issue include:
  • Symmetrix:
    • LUNs presented to two FA ports as 1, 2, and 3
    • Same LUNs presented to two other FA ports as 5, 6, and 7
    • Server A is zoned to the first two FAs
    • Server B is zoned to the second two FAs  
       
  • Clariion:
    • ESX Server A is in Storage Group X
    • ESX Server B is in Storage Group Z
    • LUNs are assigned to Storage Group X as LUNs 1, 2, and 3
    • The same LUNs are assigned to Storage Group Z as LUNs 5, 6, and 7

Solution

The LUNs presented to a set of servers must be presented with the same set of LUN numbers to all hosts.
 
For the above sample configurations:
  • Symmetrix - Present the LUNs to all FAs to use the same LUN numbers.
  • Clariion - Use a single Storage Group and add to it all ESX host that will access the LUNs assigned to that Storage Group. This always presents the same HLU (Host Logical Unit) number to all hosts in the same Storage Group.
  • Other Arrays - Use an equivalent process to maintain the same LUN numbers presented to all hosts that will share it.
If this is not possible, see the SAN Configuration Guide for your version for ESX/ESXi for a solution. This solution is presented below for your convenience, with updates from August 9, 2006 that correct some issues in the original text.

Issues with Offline VMFS Volumes on Certain Arrays

On some arrays, it may not be possible to display the LUN with the same LUN ID across hosts. As a result, the ESX Server system incorrectly detects the LUN as a snapshot and places it offline. Examples of storage arrays for which the same LUN ID may not be visible for a given LUN across hosts are Clariion AX100 and few IBM TotalStorage Enterprise Storage Systems (previously Shark Storage systems).

Note: If you use Clariion AX100 with Navisphere Express, you cannot configure the same LUN ID across storage groups. You must instead use a version of Navisphere software that has more comprehensive management capabilities. For more information regarding Navisphere, please consult EMC support and documentation.  For IBM TotalStorage 8000, you need to recreate these LUNS.  For more information regarding IBM TotalStorage, please consult IBM support and documentation.  

To resolve issues with invisible LUNs on certain arrays:

  1. In VMware Infrastructure Client, select the host in the inventory.
  2. Click the Configuration tab and click Advanced Settings.
  3. Select LVM in the left panel and set LVM.DisallowSnapshotLUN to 0 in the right panel.

    Warning:
    When LVM.DisallowSnapshotLUN is set to 0, no snapshot LUNs should be presented to the ESX host. Otherwise, data corruption may result. For details, see State 3 - EnableResignature=no, DisallowSnapshotLUN=no in the SAN Configuration Guide for your version for ESX/ESXi.
     
  4. Rescan all VMFS volumes.
After the rescan, all VMFS volumes are available.

Additional Information

For translated versions of this article, see:

Tags

snapshot-lun lun-presentation

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