Expanding Physical compatible RDMs

[wstclair44]

I have some RDMs that are a part of a Microsoft cluster that I need to grow. These RDMs are in Physical compatibility mode. I am reading VMware KB: Expanding the size of a Raw Device Mapping (RDM) on step 11 it says add the RDM back to the VM as new disk and select virtual compatibility mode.

If these RDMs were previously in physical compatibility mode why would I add them back in Virtual compatibility mode?

Is this KB in-correct and should it say either virtual or physical mode?

[kastlr]

Hi,

when using pRDM's VMware will initially create the *.vmdk file which does contain the disk geometry of the physical disk.

When you now expand the physical disk in your array that change is immediately visible to the VM.

But the *.vmdk will still contain the old geometry and therefor the old size.

I was involved in an issue where a customer who did expand a pRDM run into an issue several weeks later when the VM tries to write to the newly added space.

That's why you should represent an expanded pRDM in the way described in the VMware article.

Regards,

Ralf

[rcporto]

I think the step 11 was a typo, since on step 13 you can see: select virtual or physical compatibility mode.

[kastlr]

Hi Richardson,

IMHO this isn't a typo, as the procedure is written for RDM's used by a virtual cluster.

Therefor the steps differ for Node B.

Regards,

Ralf

[rcporto]

Sorry, but if this is not a typo, do you think the cluster will works with devices in different compatibility mode ?

[kastlr]

You're right, my fault.

Thanks for the clarification.

Regards,

Ralf