LUN mapping

[compendius]

We have a SAN with some large data volumes currently exported over FC to some physical servers.

We are looking at virtualising these servers with VMware VSphere.

What we want to be able to do is create a VM of a server, and then once it is up and running literally map the LUN holding the relevant data volume from the SAN to the virtual server. So effectively the LUNs containing the data volumes on the SAN are then just be remapped to the new VM from the old physical server box.

Can anyone explain if LUN mapping is possible in the above context with vSphere....?

The reason VSphere is on the cards is that Citrix Xenserver 5.5 does not support LUN mapping. On Xenserver you would have to create a VM of a server, create a storage repository of a brand new LUN on the SAN, format it, and then copying the large amount of volume data from the old LUN holding the volume to the SR on the VM. This would be very time consuming.

[Duncan Epping]

Yes it is and it is called a "Raw Device Mapping" (RDM). It's just a couple of clicks in the vSphere Client.

Duncan

VMware Communities User Moderator | VCP | VCDX

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[Simon Zhang]

yeah, RDM is the solution here, you only need to map these luns to VMware VSphere; so far FC luns mapped directly to VM not supported yet

binoche, VMware VCP, Cisco CCNA

[Rumple]

We have a SAN with some large data volumes currently exported over FC to some physical servers.

As long as those data volumes are 2TB-512bytes you should be ok....

[compendius]

Hi,

Thanks for all of your answers. I am now confused, as they seem to contradict themselves.

Can someone clear up whether Raw Device Mapping works on vSphere over Fibre Channel from a SAN LUN directly to the virtual machines?

Also can someone confirm the maximum size of the LUN over Fibre Channel with RDM.

[Rumple]

Rdm max is still 2tb-512 bytes

As for zoning directly to the vm, I though that was possible using npiv...

[mcowger]

Even with NPIV you still have to mask/zone the LUN to the NPIV address as well as the addresses of the hosts.

But yes, RDMs do what you are looking for, and are limited to 2TB.

--Matt

VCP, vExpert, Unix Geek

[Simon Zhang]

yeah, npiv still have the limitation that fc luns also need to map to vsphere hosts

binoche, VMware VCP, Cisco CCNA

[compendius]

Thanks for clearing it up.

[compendius]

To give some feedback...

ESX Server v 3.5

I created a FC LUN on my IBM DS4800 SAN.

I mapped that to the HBA on the box that was going to host the ESX server.

I installed Vmware ESX server (HPDL385 G2 2 dual core opteron 12 GB ram) on the local server disks.

I installed Windows Server 2008 R2 as a VM. During the VM setup I had a choice for RDM. I selected this and immediately could see the LUN on the SAN.

So the Windows VM installed on the SAN.

I then created another LUN on the SAN to add another hard drive to the Windows Server.

To get the Windows VM to see the new LUN, I downed the VM. Rescanned the FC HBA on the ESX server on storage adapters/configuration TAB (right click adapter and rescan).

I then went to the VM settings and added a new hard drive as an RDM. It could immediately see the new LUN.

I started the Windows VM up again and there was the new hard drive.

Very easy and user friendly.