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I recently had to connect two 4TB sata disks to a server to provide some raw storage to the network. Going on past experiences I didn’t want to virtualise the disks but rather present them to the virtual machine guest as a raw device mapping (RDM).

You will need a separate datastore that is separate to the ones you are attaching. It will have to be VMFS5 to get around the 2TB limit with VMFS3.

Note: This is not supported by VMware to the best of my knowledge.

Procedure

  1. Start a SSH session to the VMware ESX host (or if on the physical server, drop to console)
  2. Run fdisk to see the disk layout.
fdisk –l
vmware_esx_fdisk_list
  1. You will need to find the vml identifier, you need to match that to the drive.
ls /dev/disks/ -l
VMware_ESX_ls_dev_disks

In my example, the two I am interested in are:

vml.01000000002020202020202020202020205a33303346325742535434303030

vml.01000000002020202020202020202020205a33303351523246535434303030

  1. Now browse to the VMFS5 datastore you will be creating the RDM’s
cd /vmfs/volumes/datastorename
Browse to RDM location
  1. Best practise would be to create a folder for the RDM’s to sit in
mkdir RDMs
  1. Create the RDM’s by running the vmkfstools command (use the vml. location that you found in previous steps)
vmkfstools -r /vmfs/devices/disks/vml.01000000002020202020202020202020205a33303346325742535434303030 4TB_Disk1_RDM.vmdk -a lsilogic
vmkfstools -r /vmfs/devices/disks/vml.01000000002020202020202020202020205a33303351523246535434303030 4TB_Disk2_RDM.vmdk -a lsilogic
VMware_ESX_vmkfstools_RDM
  1. Verify you have the files created
ls –lash
VMware_ESX_RDM
  1. Attach to virtual machine
VMware_Use_Exisiting_Virtual_Disk VMware Select RDM VMware_RDM_Attached VMware RDM_Physcial_LUN

Should you have any questions, comments or suggestions, please don’t hesitate to comment below. If you like what you have read, please share it on your favourite social media medium.

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