I recently attempted to setup a virtual machine inside ESXi and I'm trying to get it to have access to an entire secondary drive in the server for data storage and whatnot.
When I go into 'Add Hardware' and select hard disk, I'm presented with three options:
- Create a new virtual disk
- Use and existing virtual disk
- Raw Device Mappings
By obvious choice I'd want to use raw device mappings, but it is greyed out. I've tried this guide to create a fake virtual disk that points to a raw drive uuid but this yielded no working results.
I would much rather not create a virtual disk the entire size of the drive as a) I can't truly acheive a virtual disk the full size of the drive and b) there is increased overhead using a virtual disk instead of a raw device mapping (so I'm lead to believe at least).
While it is a single un-raided mechanical drive, it offers just the amount of performance I require from it on it's own. I feel that by using a raw device mapping would yield the best read/write speeds of the drive and also would be convenient to be able to remove the drive for use in another computer to read the data thats on it – rather than having to go through a .vmdk file to access stuff should this be required for any reason.
Many thanks!
Best Answer
AFAIK RDM does not need VT-d to work unless something has changed since v 5.0 when I last used a Raw Disk Mapping on ESXi.
You don't passthrough the controller to need VT-d. Only the drive.
Regarding the greyed out option for RDM that's probably because you use the desktop vSphere client instead of the Web client (which fully supports RDM).But even without the web client you can manually create the RDMs via SSH.
The procedure is described on the KB article pou posted. As far as I remember that procedure works.
What exactly doesn't work for you?
Regarding not mapping the entire drive I believe that is not possible.
Raw Disk Mapping is just that. RAW mapping of the drive to a VM.
Regarding the performance, unless you have a very specific workload that doesn't do well on top of VMFS, there isn't any significant gain by using RDM IMHO.
Update:
It turns out I was wrong about RDM support in the Web Client. Both desktop and web client support RDM but only for SAN LUNs, not for local disks.
So, to do a Raw Disk Mapping of a local disk you need to do it manually via SSH.
The KB article (KB1017530) describes the procedure quit well now that I read it all again.
It also mentions that this may not work on some controllers.
What is your hardware exactly? Controller Chipset?
Personally when I first tried to do a raw disk mapping I used this tutorial http://www.vm-help.com/esx40i/SATA_RDMs.php
Maybe this will help you better.