VMware Raw Disk Mapping Conversion

It’s been bothering me for a long time how to convert Raw Disk Mappings to traditional VMDK files.

I came into an environment where RDM’s where used for any drive other than the System Drive. I didn’t’ understand it when I first started here.  But after a lot of research I realize it may have been done by someone who read this document:


The document does recommend that someone can create RDM’s for an improvement in VM performance. For me it’s a management nightmare, My SAN now has LUNs specifically for one drive on VM.

I decided to start converting them to consolidate the amount of LUNs I have and to also consolidate the amount of Disk Groups.

The most effective way I found was to shut down the VM and do a Clone of the original.  This requires down time but, is well worth the outage IMHO. The other way to do it would be to do a V2V using converter.  I haven’t tested that avenue yet. When the clone is made the RDM’s are removed from the VMs.

This has now made management and consolidation much easier. If anyone has any suggestions on how to gauge performance on something like this please leave a comment below or send me a message on twitter @JimPeluso

If you’d like more details on MSCS support in ESX and vCenter follow the link below:





2 thoughts on “VMware Raw Disk Mapping Conversion

  1. As you’re already well aware the RDM performance differential has diminished significantly since the referenced white paper was released. I’m with you in elimination of them in most cases, and was on the same mission to do so when I had them.

    Have you attempted to use vmkfstools to do the conversion with the server online? I have not had the opportunity but would love to see it in action!

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