PowerFlex Raw Device Mapping for Local Storage
Summary: This KB article describes how to do Raw Device Mapping (RDM) to the PowerFlex virtual machine (VM) in ESXi. This article can be used only if the ESXi server has a Redundant Array of Independent Disks (RAID) controller. If not, it might cause a "purple screen" to the ESXi and reboot. ...
Instructions
Steps: This is the VMware KB for the procedure: Configuring Raw Device Mapping (RDM) for local storage (External Link)
Symptoms:
These symptoms appear when attempting to configure a local datastore as a Raw Device Mapping (RDM):
- The option to create an RDM is grayed out.
- You cannot add a local volume to a virtual machine as a raw device mapping.
Cause: By default, local storage devices are disabled as potential RDM candidates on an ESXi/ESX host. This is due to most existing local controllers not meeting the hardware requirements to correctly address and communicate with RDM disks.
Resolution:
Both of the following conditions are required to configure an RDM on local storage with ESXi/ESX hosts:
- The candidate device must support SCSI Inquiry Vital Data Product (VPD) page code
0x83, which is used to directly address and communicate with RDM devices. For more information about SCSI sense code, see Interpreting SCSI Check Conditions in VMkernel logs - The candidate device must export a global serial number, which enables the ESXi/ESX host to uniquely identify the device for use as an RDM.
This capability to serve as an RDM may not be possible on some local controllers and their attached storage. Contact your hardware vendor to verify if your controller supports the required conditions, and for any technical support.
If you have a suitable controller, you can configure the local device as an RDM. Configuration of a local storage device as an RDM must be done using the Command-Line Interface (CLI), it cannot be done through the vSphere Client.
To configure a local device as an RDM disk:
- Open an SSH session to the ESXi/ESX host.
- List the disks that are attached to the ESXi host, use the command:
# ls -l /vmfs/devices/disks
- From the list, identify the local device you want to configure as an RDM and copy the device name.
The device name will likely be prefixed with t10. And look similar to:t10.F405E46494C4540046F455B64787D285941707D203F45765 - To configure the device as an RDM and output the RDM pointer file to your chosen destination, run the command:
# vmkfstools -z /vmfs/devices/disks/ /vmfs/volumes///_x.vmdk
For Example:
# vmkfstools -z /vmfs/devices/disks/t10.F405E46494C4540046F455B64787D285941707D203F45765 /vmfs/volumes/Datastore2/SVM-1/svm-1_1.vmdk
The size of the newly created RDM pointer file appears to be the same size as the Raw Device to which it is mapped. This is a dummy file, and it does not consume any storage space.
- When you have created the RDM pointer file, attach the RDM to a virtual machine using the vSphere Client:
-
- Right-click the virtual machine that you want to add an RDM disk to.
- Click Edit Settings.
- Click Add….
- Select Hard Disk.
- Select Use an existing virtual disk.
- Browse to the directory that you saved the RDM pointer to, select the RDM pointer file and click Next.
- Choose the virtual SCSI controller that you want to attach the disk to and click Next.
- Click Finish.
You should now see your new hard disk in the virtual machine inventory as Mapped Raw LUN. As this virtual machine now has an attached local disk migration, using vMotion is not possible.