Author Topic: Physical RDM Setup  (Read 608 times)

Offline Skirge01

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Physical RDM Setup
« on: February 03, 2018, 12:43:52 am »
I recently came across this article about the best way to set up ESXi for use with FlexRAID (tRAID in my case):  http://flexraid.com/2014/02/07/storage-deployment-vmware-esxi-iommuvt-d-vs-physical-rdm-vs-virtual-rdm-vs-vmdk/

I'm using the common LSI 9211 adapters flashed to IT mode. I currently have two of these controllers in passthrough mode to the VM which is running the tRAID software. I'm considering switching over to Physical RDMs as Brahim suggests in the article I referenced, but all my disks are currently showing as "Local ATA Disk" devices, which that article says means the controller does not support Physical RDMs. Is this simply because my controllers are currently in passthrough mode?

Thanks in advance.

Note: If you think you saw this before, I mistakenly posted it in the RAID-F General forum and deleted it moments ago.

Offline Brahim

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Re: Physical RDM Setup
« Reply #1 on: February 03, 2018, 10:28:03 am »
No need for RDM if you are passing the controller to the VMs. RDMs are for when ESXi has the controller non-pass-through.

Offline Skirge01

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Re: Physical RDM Setup
« Reply #2 on: February 03, 2018, 12:11:54 pm »
Right, but, as you point out in the article I mentioned, this limits your ESXi options in various ways, such as not being able to use snapshots. Additionally, my understanding is that managing your storage in ESXi is much easier when you're using RDMs. I also wonder whether passthrough or RDM is more efficient.

Offline Brahim

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Re: Physical RDM Setup
« Reply #3 on: February 04, 2018, 06:49:02 pm »
Ah, now I follow you.
If you have followed the steps in "Setting up Physical RDMs", rebooted, and your disks are still showing up as "Local Disk", then the controller is not supported.
Now, whether you should go back to passing through the controller or doing Physical RDMs the unsupported way (using vmkfstools) is a toss. I ran Physical RDMs using the unsupported way for years without issues, but that was 10 years ago and not something I would recommend these days. It is just not worth it since supported controllers are fairly cheap.

So, me, I would do Physical RDMs (supported or unsupported). You, only do Physical RDMs the supported way. :)