RDM versus VMDK devices performance on Ubuntu VM

Question

I want to use some devices on a Ubuntu VM in VMWare environment. I have a choice of using them as RDM or VMDK. I was originally thinking of using them as RDM due to performance benefits. However I am running into some issues due to compatibility (somewhere in the software-hardware stack of ubuntu version, ubuntu kernel version, driver, motherboard, disks etc.). While I was trying to find out about performance difference between RDM and VMDK, I am coming across a lot of information stating that there isn't much difference between the two as of now, however most of those postings are for specific configurations.

I want to know is there still significant performance benefit of using a raw linux block device in RDM mode as opposed to a VMDK?

Answer 1

From my experience, I replaced RDM's with VMDK's in a MS-SQL server running in production and it worked fine. Also, using VMDK gives you a lot of flexibility with your devices, that's a big plus.