Raw Device Mappings Option Grayed-out?

[z1b903]

Overview- ESX3.5/Virtual Center 2.5. HP Bladesystem C3000/BL680 Blade server running ESX3.5. Storage is a HP AIO 1200, this is a NAS devices running Windows Storage Server 2003 (with the Microsoft iSCSI initiator software). VLAN dedicated to iSCSI traffic, and separate Vswitch in ESX3.5 for Vmkernel. The NAS iSCSI configuration defines 3 major LUN's (Raid10, Raid5, Test raid10). ESX3.5 sees all 3 Lun's, and the storage can be added via the add storage wizard.

I need to utilize the Microsoft Volume Shadow Service on the AIO 1200 NAS device. I was hoping to use the RDM capability to do this, but when I attempt to create a "Disk" for a new guest (or add a disk for an existing guest) with the add hardware wizard, the Raw Device Mappings option is "Grayed-out" and not selectable.

In general I can create Guest VMDK at will, but the option to create a Raw Disk Mapping LUN is not selectable.

I sense I am making a mistake in the process of actually adding the storage to the ESX3.5 server, but here again, the "wizard" seemingly goes ahead and creates a VMFS files system on the Lun when it is added to the ESX.35. server (this is confirmed by examining the VMFS directory from AIO 1200),

How does one create a RDM disk resource?

[mike_laspina]

Hi,

The RDM mapping is a pointer in the VM and ESX server configuration files to a Raw block device . It must be an unassigned raw LUN. If it was formatted as vmfs it will not be available until you delete it and rescan for storage twice in a row.

[kjb007 · Accepted solution]

As Mike stated, you have to have an unassigned LUN to create an RDM out of. From your description, you have 3 LUNs, which are in use. You will have to create a new LUN, make sure it is seen by the ESX hosts, and then try to add the disk to the VM's. If the option is grayed-out, it will mean that the ESX server does not see any unused LUNs that it can use to create the device.

-KjB

[z1b903]

Folks:

Ah ha makes sense now, I'll give it a try, and let you know what the result is.

Mark M.

[z1b903]

Folks:

Worked like a charm. I now have RDM capability. Mike I'm sorry I'm new to the Forum interface, and thought I caould give both you and the other person the "correct" answer, but alast this is not so. My mistake..

Mark M.

[mike_laspina]

No problem. Good to hear it's working.

[kjb007]

You can always leave another helpful. ; -)

-KjB

[NHATech]

I have a simular problem except in my case the RDM mappings were OK originally but were deleted on one of the cluster nodes. I am trying to re-create the mappings but I do not have the option of selecting the luns. The other node of the cluster (the one that is still working) has been shut down, yet I still do not have the option of selecting the luns.

[kjb007]

Run a rescan on your hba's a couple of times. Then, make sure the LUN is still made available to the ESX host from your SAN. Then go back in and try to re-map.

-KjB

[akash1980]

Guys,

Help required.

We are planning to virtualise a server which got SAN storage (200 GB) attached.

Instead of vitalizing the disk which is using SAN space, I am thinking to present that particular disk as a RDM to VM.

• Is it feasible?

• Any challenges?

• Do I need to un-map the LUN from Physical server first inorder to present to VM as a RDM?

• I assume, just I need to present the same LUN to different ESX hosts in cluster to use DRS/Vmotion, Is it true?

• Best practices?