How do I setup a RDM?

[-_DK_-]

I feel lame asking this question, but I can't find anything that clearly explains how to do this.

Environment:

2 ESX 3.5u1 servers

1 VC 2.5

Current ESX LUNs are through iSCSI

I have iSCSI LUNs connected via the guest OS using MS iSCSI software initiator, but want to try using RDM for experimental purposes at this time.

I've created a new LUN and assigned it to the ESX servers, and it shows up in Storage. But when I go to add a disk to the guest OS, the option for "Raw Device Mapping" is greyed out. It seems that I need to enable RDMs, or do something else with the new LUN or the ESX server, but can't find any documentation that says "check this box" or "modify this file".

Thanks

-=DK=-

[weinstein5]

There is not really anything you need to enable for RDMs to work but you do need to have LUNs that are not formatted as VMFS - Did you format the LUN for VMFS? You have to make sure the LUN is not formated for VMFS

[-_DK_-]

I tried both ways.

First I connected the LUN to the ESX host so it only appears under Storage Adapters, then tried adding the disk to my guest, but RDMs were greyed out.

So I formatted it and added it to Storage, and the option was still greyed out.

[TomHowarth]

RDM mappings to iSCSI LUNs require that pointer files are created on a VMFS file system that then reference the iSCSI LUN mapped to the host. If the datastore in use happened to be NFS, then RDM pointers can't be created, and thus can't be used.

If you are trying to direct map, then you do not need to present to the host, just make sure that your Guest can see the iSCSI network and can be authenticated to the iSCSI target

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Tom Howarth

VMware Communities User Moderator

[beckham007fifa]

I am a layman in this , could you please help me out in doing this. I am facing problem with vmfs volumes for MS cluster. I have logged call to VMware support team and they said they will not give support unless until we have RDM for MS cluster. I am thinking of doing with RDM and need help.

[MauroBonder · Accepted solution]

check this kb, maybe helpful http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100461...