VMware Vsphere raw device mapping

    Raw Device Mappings

    What is raw device mapping?

    Raw device mapping is a feature where the virtual machine can directly access the storage devices such as SAN or DAS.

    With a VMware we will use vmdk pointer to provide the proxy facility to raw device.

    In a virtual environment some cases we may need to have a raw device mappings.

    Why we need raw device mapping?

    • To configure Microsoft failover cluster, we can configure raw device as shared storage.
    • When we are configuring Microsoft failover cluster with one node is running on as a VM & other node/s running as a physical.
    • To run some of the san management software(ex hitachi horcm)
    • To run some backup software on virtual machine, and needs to get storage level backup

    How to Configure?

    1. Here I have one vm which is prepared to mount raw device


    1. Using new datastore adding procedure, we can see new lun which is provided from our shared storage(in my case im using windows iscsi server)


    1. Go to add hardware wizard of virtual machine and select hard disk


    1. Select “Raw Device Mappings”


    1. Select the Raw device lun


    1. We can select location for VMDK pointer(raw device mapping pointer)


    1. There are two options
      1. Physical
      2. Virtual- In a virtual mode we can take the snapshots




    1. With physical mode of the raw device, we cannot take snapshots.


    1. We can see vmdk pointer which is used to proxy our raw lun in our datastore.



    10 . With a virtual mode we can take the snapshots


    1. If want we can change the multipathing policy as same as datastore



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