How To Identify Virtual Machines Having RDM disks in VMware?

In this blog we will have a look on How To Identify Virtual Machines Having RDM. Let’s understand about VMware RDM.

VMware RDM

VMware RDM is a mapping file in a separate VMFS volume that acts as a proxy for a raw physical storage device. The RDM allows a virtual machine to directly access and use the storage device. It enables a storage LUN (Logical Unit Number) to be directly presented to a virtual machine from the storage array. LUN is a unique alphanumeric number of the storage unit. To know more about RDM, visit our blog post What is VMware RDM?

RDM disks are looks like regular VMFS disk in vSphere. Sometimes you need to identify that which hard disk is RDM disk. The LUN used for RDM purpose have the unique identifier or NAA ID that helps us to identify the RDM disks. There are many ways to know the RDM disk information but I am going to discuss about two main methods.

Identify VMware RDMs using the vSphere Client

  1. Connect to vCenter Server or a host using the vSphere Client.
  2. Select a Virtual Machine.
  3. Right-click| Click on Action button the virtual machine and click Edit Settings.
  4. Select each hard disk in the Virtual Hardware list with a summary Mapped Raw LUN. The path to the RDM virtual disk mapping file and the name of the backing SCSI device are listed. It will start with vml.xxxxxxx.

Identify VMware RDMs using the ESXCLI

  1. SSH to the ESXi host on which the virtual is hosted.
  2. Run the following commands
Get-VM | Get-HardDisk -DiskType "RawPhysical","RawVirtual" | Select Parent,Name,DiskType,ScsiCanonicalName,DeviceName | ft

3. It will give you a list of VMs having RDM disks hosted on the same ESXi host.

There are other commands available such as:

Get-VmRdm | ft

That needs to run from the VMs on which you are checking RDM disks. But sometime this commands would not work depending on the situation. The best option is ESXiCLI to check the RDM disks in VMware Virtual Machines.

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