Virtualization Articles and Resources

Rapid Cloning Utility v2.1 Frequently Asked Questions (FAQ)


Q: What is new in 2.1?

A: The following...

New datastore management features include;

  • Provision new NFS or VMFS datastore to all hosts in a Datacenter, a Compute Cluster or an individual Host
  • Resize NFS datastore (grow and shrink!)
  • Manage Deduplication

New cloning features include:

  • Support for rapid cloning of VMs to VMFS
  • Control over which datastore each vmdk file within a VM is cloned into

New integration features include:

  • Automatic import into VMware View
  • Manual import into Citrix XenDesktop

New configuration features include:

  • The ability to specify which components of the controller should be accessible to RCU

The RCU 2.1 also includes a programmable API.

Q: Where are these features exposed?

A: Directly in the Virtual Center Client.  Please see the screenshot below.

Q: Where can I get the 2.1 version of the Rapid Cloning Utility?

A: The Rapid Cloning Utility is available from the ‘Download Software’ page on

Q: Is it true that this version configures iSCSI on the ESX hosts?
A: Yes.  The idea here is to save the administrator time and reduce the chances of misconfiguration that are possible when performing this repetitive task (on each host).  When a new iSCSI datastore is requested, the RCU will enable and configure iSCSI on each of the ESX servers selected.  The RCU does not create the required network interfaces though, so these need to be configured first.

Q: When provisioning and cloning VMFS datastores, does the RCU configure the ESX host to use the most preferred path?
Yes.  In the case of iSCSI, lun access is balanced across all available interfaces.  In the case of FCP, lun access is balanced across all preferred paths.

Q: Can I clone VMs that have snapshots in RCU 2.1?
Yes.  The only caveate is that the first clone operation performed will be a VC native clone.  All subsequent clones will use the rapid cloning method.

Q: Cloning to an existing VMFS datastore or a single new VMFS datastore seems to exhibit the same speed as native VC cloning.  Why is this?
The largest difference between RCU cloning in VMFS and NFS is; when cloning in NFS the RCU can leverage File Level Flexclone to speed up VM creation (to the tune of 3.5GB/s or higher).  This will be available for VMFS when VMware releases the vStorage APIs for Array Integration (VAAI) in a future version of ESX/ESXi.  Until then, the RCU speed advantage can be obtained by cloning the datastores.  This is done by selecting the option to create new datastores, then creating more than 1.

Q: How many VMs can RCU create?
This depends entirely on the number, size and available resources on the vCenter and ESX servers.  Please see the VMware ESX Configuration Maximums guide for details.

Q: What if I create too many VMs?
We’ve found in our testing that once ESXi 3.5 has too many registered VMs, it disconnects from the VC and will not rejoin.  The workaround we used to address this was:
1.) Completely remove the ESXi 3.5 server from the VC server
2.) Use the Datastore Destroy (NetApp RCU feature) to deallocate the LUN
3.) Reboot and add back the ESXi 3.5 server

Q: Is the RCU 2.1 a supported product?
Yes, version dependancies are in the Release Notes.

Q: Does the RCU 2.1 work with vSphere?
vSphere support is considered experimental at this time.  A PVR can be filed for support.

Here is a breakdown of what 'works':

VMware vCenter Server 4.0 managing ESX 3.5 hosts : all features

VMware vCenter Server 4.0 managing ESX 4.0 hosts : only NFS features

Q: What version of Data ONTAP do I need?
Data ONTAP version or higher is required.

Q: Where can I find information on the API?
The API documentation is in an appendix of the Installation/Administrator Guide.  Samples have been posted here.

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