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Putting Some VMware ESX Storage Tips Together | Part 2

Making an internal SATA HDD into an RDM for a Windows-based VM

In the first part of this post I showed how to use a tip from Dunacn Epping to fake VMware into thinking that a HHDD (Hybrid Hard Disk Drive) was a SSD.

Now let's look at using a tip from Dave Warburton to make an internal SATA HDD into an RDM for one of my Windows based VMs.

My challenge was that I have a VM with a guest that I wanted to have a Raw Device Mapping (RDM) internal SATA HDD accessible to it, expect the device was an internal SATA device. Given that using the standard tools and reading some of the material available, it would have been easy to give up and quit since the SATA device was not attached to an FC or iSCSI SAN (such as my Iomega IX4 I bought from Amazon.com).

Image of internal RDM with vMware
Image of internal SATA drive being added as a RDM with vClient

Thanks to Dave's great post that I found, I was able to create a RDM of an internal SATA drive, present it to the existing VM running Windows 7 ultimate and it is now happy, as am I.

Pay close attention to make sure that you get the correct device name for the steps in Dave's post (link is here).

For the device that I wanted to use, the device name was:

From the ESX command line I found the device I wanted to use which is:

t10.ATA_____ST1500LM0032D9YH148_____Z110S6M5

Then I used the following ESX shell command per Dave's tip to create an RDM of an internal SATA HDD:

vmkfstools -z /vmfs/devices/disks/ t10.ATA_____ST1500LM0032D9YH148_____Z110S6M5
/vmfs/volumes/datastore1/rdm_ST1500L.vmdk

Then the next steps were to update an existing VM using vSphere client to use the newly created RDM.

Hint, Pay very close attention to your device naming, along with what you name the RDM and where you find it. Also, recommend trying or practicing on a spare or scratch device first, if something is messed up. I practiced on a HDD used for moving files around and after doing the steps in Dave's post, added the RDM to an existing VM, started the VM and accessed the HDD to verify all was fine (it was). After shutting down the VM, I removed the RDM from it as well as from ESX, and then created the real RDM.

As per Dave's tip, vSphere Client did not recognize the RDM per say, however telling it to look at existing virtual disks, select browse the data stores, and low and behold, the RDM I was looking for was there. The following shows an example of using vSphere to add the new RDM to one of my existing VMs.

In case you are wondering, why I want to make a non SAN HDD as a RDM vs. doing something else? Simple, the HDD in question is a 1.5TB HDD that has backups on that I want to use as is. The HDD is also bit locker protected and I want the flexibility to remove the device if I have to being accessible via a non-VM based Windows system.


Image of my VMware server with internal RDM and other items

Could I have had accomplished the same thing using a USB attached device accessible to the VM?

Yes, and in fact that is how I do periodic updates to removable media (HDD using Seagate Goflex drives) where I am not as concerned about performance.

While I back up off-site to Rackspace and AWS clouds, I also have a local disk based backup, along with creating periodic full Gold or master off-site copies. The off-site copies are made to removable Seagate Goflex SATA drives using a USB to SATA Goflex cable. I also have the Goflex eSATA to SATA cable that comes in handy to quickly attach a SATA device to anything with an eSATA port including my Lenovo X1.

As a precaution, I used a different HDD that contained data I was not concerned about if something went wrong to test to the process before doing it with the drive containing backup data. Also as a precaution, the data on the backup drive is also backed up to removable media and to my cloud provider.

Thanks again to both Dave and Duncan for their great tips; I hope that you find these and other material on their sites as useful as I do.

Meanwhile, time to get some other things done, as well as continue looking for and finding good work a rounds and tricks to use in my various projects, drop me a note if you see something interesting.

Ok, nuff said for now.

Cheers gs

Greg Schulz - Author Cloud and Virtual Data Storage Networking (CRC Press, 2011), The Green and Virtual Data Center (CRC Press, 2009), and Resilient Storage Networks (Elsevier, 2004)

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More Stories By Greg Schulz

Greg Schulz is founder of the Server and StorageIO (StorageIO) Group, an IT industry analyst and consultancy firm. Greg has worked with various server operating systems along with storage and networking software tools, hardware and services. Greg has worked as a programmer, systems administrator, disaster recovery consultant, and storage and capacity planner for various IT organizations. He has worked for various vendors before joining an industry analyst firm and later forming StorageIO.

In addition to his analyst and consulting research duties, Schulz has published over a thousand articles, tips, reports and white papers and is a sought after popular speaker at events around the world. Greg is also author of the books Resilient Storage Network (Elsevier) and The Green and Virtual Data Center (CRC). His blog is at www.storageioblog.com and he can also be found on twitter @storageio.