Guest iSCSI mapping vs Raw Device Mapping

Muhammed Ashraf Arummel 21 Reputation points

Dear All,

I have some LUNs which I map to a Windows server, is there an advantage to mapping the LUN via ESXi versus mapping with the iSCSI initiator on the guest?

Which method is Read-write more capable and Multipath?

Windows Server 2019
Windows Server 2019
A Microsoft server operating system that supports enterprise-level management updated to data storage.
3,444 questions
Windows Server 2012
Windows Server 2012
A Microsoft server operating system that supports enterprise-level management, data storage, applications, and communications.
1,526 questions
Windows Server
Windows Server
A family of Microsoft server operating systems that support enterprise-level management, data storage, applications, and communications.
12,090 questions
A Windows technology providing a hypervisor-based virtualization solution enabling customers to consolidate workloads onto a single server.
2,530 questions
0 comments No comments
{count} votes

2 answers

Sort by: Most helpful
  1. JiayaoZhu 3,911 Reputation points


    Thanks for posting on our forum!

    Firstly, I need to determine your production environment, VMware or Hyper-V (RDM seems to be a VMware product)? From my perspective, the choice then, is whether you wish control and management of iSCSI LUNs via the ESXi host or via the guest OS. If the latter, ESXi is only aware of your storage traffic as network traffic - it treats it and understands it as just another IP packet on the VM network setup. If an RDM through the ESXi host, you get the advantage of managing the LUNs, multipathing, and connectivity via the hosts and/or vCenter, easing many aspects of LUN management. And I see you prefer to have multipath and more capable read-write function, so I may suggest RDM. But if you are in a VMware environment, I strongly suggest you to contact their engineers directly to gain more professional information on RDM.

    Secondly, for our Microsoft, we have SMB multichannel to support clients who use our product (like Hyper-V) while have the same demand as yours. If you also use Hyper-V, you can take a look at this product:

    Finally, I found some articles comparing the pros and cons of Guest iSCSI mapping and Raw Device Mapping respectively:

    Please note: Information posted in the given link is hosted by a third party. Microsoft does not guarantee the accuracy and effectiveness of information.

    Thanks for your support! Besides, would you please help me Accept Answer. An accepted blog can be put on top of our forum, so that people who have a similar issue can get access to their solution more quickly.


    If the Answer is helpful, please click "Accept Answer" and upvote it.

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

    1 person found this answer helpful.
    0 comments No comments

  2. Alex Bykovskyi 1,681 Reputation points


    As mentioned, both options will work and you will be able to configure multipathing either on ESXi level or on Windows VM. As for performance, you shouldn't see any difference, but I would still run tests before using the configuration. StarWind VSAN for vSphere can be used as an iSCSI storage for vSphere deployments. The following guide covers the configuration process:


    Alex Bykovskyi

    StarWind Software

    Note: Posts are provided “AS IS” without warranty of any kind, either expressed or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.

    0 comments No comments