Today, we had a customer call in and tell us that they couldn't do Thick provisioning from a vCenter template. We went into vCenter (the GUI), and sure enough, we could only provision Thin virtual machines from it.
But - apparently on another vCenter cluster, they COULD provision Thick virtual machines. There seemed to be no difference between the virtual machines. Note that we are using NFS and not Block or iSCSI or Fibre Channel storage.
We went into vCenter, and lo and behold, we saw this situation...
NOTE: To get to this screen in VMWare's very cumbersome GUI, you have to click on the individual datastore, then click "Configure" then a tab called "Hardware Acceleration" occurs.
So, what we have here, is one datastore that says "Not Supported" on a host, and another datastore in the same datastore cluster that says "Supported" on the exact same host. This sounds bad. This looks bad. Inconsistency. Looks like a problem.
So what IS hardware acceleration when it comes to Storage? To find this out, I located this KnowledgeBase:
There is also a link for running storage HW acceleration on NAS devices:
Storage Hardware Acceleration on NAS Devices
When these two (above) links are referenced, there are (on left hand side) some additional links as well.
For each storage device and datastore, the vSphere Client display the hardware acceleration support status.
The status values are Unknown, Supported, and Not Supported. The initial value is Unknown.
For block devices, the status changes to Supported after the host successfully performs the offload operation. If the offload operation fails, the status changes to Not Supported. The status remains Unknown if the device provides partial hardware acceleration support.
With NAS, the status becomes Supported when the storage can perform at least one hardware offload operation.
When storage devices do not support or provide partial support for the host operations, your host reverts to its native methods to perform unsupported operations.
NFS = NAS, I am pretty darned sure.
So this is classic VMWare confusion. They are using a "Status" field, and using values of Supported / Non-Supported, when in fact Supported means "Working" and Non-Supported means "Not Working" based on (only) the last operation attempted.
So. Apparently, if a failure on this offload operation occurs, this flag gets turned to Non-Supported, and guess what? That means you cannot do *any* Thick Provisioning.
In contacting VMWare, they want us to re-load the storage plugin. Yikes. Stay Tuned....
VMWare also has some Best Practices for running iSCSI Storage, and the link to that is found at:
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