Determining if an array supports automated unmap in vSphere 6.5

Many of you will be aware of the new core storage features that were introduced in vSphere 6.5. If not, you can learn about them in this recently published white paper. Without doubt, the feature that has created the most amount of interest is automated unmap (finally, I hear you say!). Now a few readers have asked about the following comment in the automated unmap section.

Automatic UNMAP is not supported on arrays with UNMAP granularity 
greater than 1MB. Auto UNMAP feature support is footnoted in the 
VMware Hardware Compatibility Guide (HCL).

So where do you find this info in the HCL? I’ll show you here.

First, navigate to the VMware HCL – Storage/SAN Section. Click here for a direct link.

Next select ESXi 6.5, the vendor of the array, and in the features section, Thin Provisioning. Finally click on “Update and View Results”. This will provide a list of supported arrays and models. In this example, I selected DELL as a vendor. It produced a range of Compellent and EQL arrays. I choose Compellent Storage Center with Array Type FC, as shown below:

Now, if I expand on the 6.5 supported release, I can see the tested configurations, including the supported driver, firmware, multipathing and fail-over policies associated with this array config.

If I expand any of those entries, I will see the footnote entries. In this example, let me select the FW version 7.1, with 16GB FC Switch and lpfc HBA.

And there you can see the statement in the footnotes that this configuration support automatic storage space reclamation on VMFS6.

Let’s compare this to an iSCSI configuration using the same arrays. Here is the list of iSCSI Compellent configurations, once more detailing the supported driver, firmware, multipathing and fail-over policies associated with this array config.

Let’s select the 7.1 firmware version as before, and examine the footnotes:

As you can clearly see, there is no mention of automatic unmap/space reclamation support in the footnotes in this example. Therefore unsupported.  Note: Since this article was published, the HCL listing shown above has been updated to reflect the automatic unmap certifications are completed on Compellent, and are now supported!

As you can see, support statements around unmap will continue to change, so check back regularly to see whether or not your array vendor has passed the certification tests required to support automated unmap. Alternatively, speak to your array vendor to find out where they are on the certification path.