Last year I wrote an article called Automating Storage DRS & Datastore Cluster Management in vSphere 5 and I provided a pretty comprehensive vSphere SDK for Perl script to help administrators automate Storage DRS configurations. These past few months I have noticed an increase in interest on the VMTN developer forums relating to Storage DRS. Majority of the questions has been related to which vSphere API methods to use and how to use these methods for cloning VMs to datastore clusters.

If you have cloned a VM before, the underlying vSphere API method being used is the CloneVM_Task(), but when cloning a VM to a datastore cluster, a different API must be used.

In vSphere 5, VMware introduced several new API methods in the StorageResourceManager and the two specific ones relating to provisioning VMs are RecommendDatastores() and ApplyStorageDrsRecommendation_Task(). The process to clone a VM to a datastore cluster is a two step process:

1. Call RecommendDatastores() which accepts very similar input as the CloneVM_Task(). In addition, you need to specify the datastore cluster also known as a Storage Pod in the vSphere API as well as the "type" (create, clone, relocate, reconfigure), in this example we will be performing a clone operation. This method will then generate a recommendation on where to place the VM which is based on the SDRS placement engine. No provisioning will occur at this point, just a placement recommendation.
2. To perform the actual provision of the VM, you will need to call ApplyStorageDrsRecommendation_Task() which accepts a recommendation ID that was generated from the first step. Once the recommendation is applied, the provisioning of the VM will start just like it did when you called the CloneVM_Task().

Note: The RecommendDatastores() will return multiple recommendations, the best one will be first entry in the array. This is the same algorithm used when performing this same operation in the vSphere Client, it also selects the first recommendation.

Now that we understand how the APIs work, let's take a look at how we can leverage this in a script for some automation! Here is a simple vSphere SDK for Perl script called datastoreClusterVMProvisioning.pl which allows you to clone an existing VM onto a datastore cluster. You will need a system that has vCLI 5.0 installed or you can use VMware vMA 5 to run the script. You will also need to connect to a vCenter Server 5 for all SDRS operations.

The script requires 4 input parameters:

• vmname - Name of the VM you wish to clone from
• clonename - Name of the cloned VM
• vmfolder - Name of a vCenter folder
• datastorecluster - Name of a datastore cluster

Here is a screenshot of cloning an existing VM onto a datastore cluster:

The script is pretty straight forward and it can easily be adapted to include other configurations as required in your own environment.

Hopefully this gives you a better idea on how to leverage the new provisioning APIs for Storage DRS and start automating your VM deployments onto datastore clusters and get the benefits Storage DRS in your vSphere environment.