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  • 1.  Help on RDM vs Passthrough use

    Posted Feb 28, 2015 12:09 AM

    What I am trying to do is figure out / understand the best way to go about achieving usage of my internal drives.

    My setup (in case it matters)

    16GB USB - ESXi boots off this

    120 GB SSD - VM Storage (All thin provisioned)

         :Windows 2008 R2 [Domain Controller]

         :Windows 2008 R2 [Seedbox / Plex Server / Tinkering Machine]

         :RHEL 7 [Tinkering Machine]

         :vCenter Server Appliance

         : pfSense eventually (This is my next project)

    250 GB SSD - Empty

    2 TB WD Se - Currently VMFS Mapped to Plex Server machine as existing hard drive (1.81 TB)

    2 TB WD Green - Empty

    I am not concerned with using Raid at the moment (unless someone offers me some advice or major benefits at the moment)

    I am not using vFlash Cache either (I really don't know much about it / if it's worth using)

    What I would LIKE is to run a NAS software such as FreeNAS / XPEnology to make it where ALL of my VM's and my network PC's can access that storage.

    Currently I have it mapped as an existing hard drive to the 2008 R2 then through Windows sharing, sharing it out to my network and other windows VM's.

    I have all of this on the on board SATA controllers so from what I've read I cannot do a pass through as it would pass through all the ports which wouldn't work.

    Also I when I select the RDM option on the VM it does not show my hard drives inside, and the only thing I've seen is to manually do RDM through the CLI.  Though I've read it's no longer worth it to do this.

    So help please, what is the best way to make use of the hard drives and be able to share them between any of the VM's if I use my 120 / 250 GB SSD for storage?  RDM via CLI, Passthrough, VMFS and share through windows, or ?

         :If it is best to just build another small machine as a dedicated NAS then I can also go that route, or if this is powerful enough I'll just run it as is.  Just needing more information!

    Edit: Or do I need to look at a separate SATA/raid controller to provide pass through and satisfy everything I need?

    System Specs:

    Motherboard: Supermicro X10SLH-F-O

    Processor: Xeon E3-1231V3B

    Memory: Kingston 32 GB ECC

    USB Boot: Sandisk 16GB

    SSD1: Kingston HyperX 3K 120 GB

    SSD2: Samsung 850 EVO 250 GB

    HD1: WD Se 2 TB

    HD2: WD Green 2 TB

    Thanks in advance!!

  • 2.  RE: Help on RDM vs Passthrough use

    Posted Mar 01, 2015 06:01 PM

    With you current setup are you experiencing any limitations in that you cannot perform specific tasks. Or is it a case of you just want to experiment with different options?

  • 3.  RE: Help on RDM vs Passthrough use

    Posted Mar 01, 2015 07:17 PM

    It's not that I am experiencing limitations but I can only assigned a new, say, 2TB Hard drive to a specific guest OS, then from within that guest OS can I share it out.  I'd rather have it already be shared and then all of my guest OS's / networks can access it as needed.

    I was planning to use FreeNAS / TrueNAS or something similar, but after reading up a bit more, they (FreeNAS forums) are saying a big no no on RDM as data will get screwed using ZFS while mapped in ESXi, and it is best to do straight pass through, AKA invest in a PCI-E card and passthrough that card and attach my TB drives to that.

    I just can't get my head wrapped around why.

         :I have 2 SSD's (120 GB / 250 GB) that will store my VMs, connected to the mobo's sata ports, along with my (current) 2x2TB hd's, but the only way for them to be used is to format them with VMFS then make them be accessed by the guest OS.  According to FreeNAS forums it's a no no.

    So either I have to invest in another PC to become a dedicated NAS, or invest a bit more in a PCI-E controller card to passthrough the HDs for proper access by something like FreeNAS.

         :Not saying my PC is a beast, but the hardware in it is plenty to run 2x Windows 2008, Linux, PFSense, and I would THINK that FreeNAS wouldn't be any big deal as well.

    I'd like to be able to take say 4x2TB drives and put them in Raid 5 and have all of my VMs / family network PCs be able to access them at any given time from my ESXi box.

  • 4.  RE: Help on RDM vs Passthrough use

    Posted Mar 01, 2015 08:50 PM


    What i understand from you HW spec is it a small PC based Server, may you are planning to run a test environment.

    If you want to use this disk as PassThrough you can buy an external HDD Case and connect to the USB and PassThrough the USB to your Guest VM, But beware you can attach this disk only on one VM.and also you will not have redundancy

    alternatively you can also look into OpenFiler or if you are some experiance in NetApp or interested in learning Netapp you can download install a Netapp Simulator

    Hope this address your question.



  • 5.  RE: Help on RDM vs Passthrough use

    Posted Mar 01, 2015 10:22 PM

    Yes, I am planning to have it be a test environment / home lab, and I'd prefer to stay away from the USB port as I am only using internal sata drives (SSD / Non-SSD)

    Now what will OpenFiler / NetApp do for me as far as enabling access to the disks directly instead of making them VMFS formatted and attaching it to that guest OS?

    I understand that OpenFiler / NetApp can share it, but how is this better or different than when I asked above as far as using something like FreeNAS?

    Edit: I am not pushing for FreeNAS, I am just asking how is it going to be any different using OpenFiler/NetApp without actually passing through a controller to enable total access to the disks, or is that even necessary...?

  • 6.  RE: Help on RDM vs Passthrough use
    Best Answer

    Posted Mar 02, 2015 02:54 PM

    Have a look at these two articles they explain how to map local disk as an RDM

    Creating RDMs on SATA drives

    Have a look at Nexenta Community Edition. You can download a VM version of it. It will allow you to create a NFS share which you can just add extra disk to over time . It also supports SSD cache if I am not mistaken.

    You also have the option of using you Windows server as a NFS server.