Planet Malaysia Blog

VMware ESX Server offers two choices for managing disk access in a virtual machine—VMware Virtual Machine File System (VMFS) and raw device mapping (RDM). It is very important to understand the I/O characteristics of these disk access management systems in order to choose the right access type for a particular application. Choosing the right disk access management method can be a key factor in achieving high system performance for enterprise-class applications.

Basically you can read few VMware RDM related guide from VMware such as: http://www.vmware.com/pdf/esx25_rawdevicemapping.pdf and http://www.vmware.com/resources/techresources/1040

I would like to share “How to add a raw mapping device on VMware” in my VMware ESX development box together with SuSE Linux Enterprise Server 9 VMware guest.

• Click on SLES 10 VMware guest in my Virtual Infrastructure Client
• Click Edit Setting
• Click Add
• Select Hard Disk
• Click Next
• Selecet Raw Device Mappings
• Click Next
• Select Target LUN
  /vmfs/devices/disks/vmhba0:0:16:0
  /vmfs/devices/disks/vmhba0:0:22:0
• Click Next
• Select Store with Virtual Machine OR Specify datastore
• Click Next
• Select Compatibility
• Choose physical (allow the guest operating system to access the hardware directly. Taking a snapshot of this virtual machine will not include this disk)
• For Virtual (it’s allow the virtual machine to use VMware snapshots and other advanced functionality
• Click Next
• Select Virtual Device Node -> SCSI (0:1)
• Click Next
• Ready to Complete
• Click Finish
• Click OK

Done!

As you can see from pictures show above, SLES 9 with 200G Raw Device Mapping Drive created.

SSH to SLES 9 and type:

rescan-scsi-bus.sh
cat /proc/partitions

You should be able to see new RDM drive and you can continue with fdisk or configure raw disk.

Additional Tips:
How to check VMware ESX version?
SSH to VMware ESX Server, type:
vimsh -n -e ‘hostsvc/hostsummary’ | grep fullName

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