VMware VAAI and Sub-LUN Clones – A hidden gem

NetApp Data ONTAP (DOT) 8.1 introduced a lot of new functionalities and optimizations. For me, one of the best ones is introduction of sub-lun cloning when used in conjunction with vStorage APIs for Array Integration (VAAI) for SAN in environments running vSphere 4.1 or higher. The same functionality is available even for Hyper-V through our Power shell and System Center Orchestrator integration.
Originally in case of LUNs, NetApp Virtual Storage Console used the standard copy within the LUN followed by LUN level cloning to achieve fast speeds and space efficiency. Starting 8.0.1, it started to accelerate the cloning with in the LUN using copy offload primitive in VAAI. With 8.1 it took a step further and started utilizing Sub-LUN cloning in environments where both VAAI and FlexClone are enabled to make sure that cloning with in the LUN is space efficient as well.

So what is a Sub-LUN Clone?


Sub-LUN clone was introduced in Data ONTAP 7.3.1 as part of FlexClone, which added new functionalities of cloning at File and Block level granularity in addition to Volume level clones. What it really does is that it allows customers to clone an individual files within a LUN. All that one needs to specify is the address in Logical Block Addressing (LBA) format. The advantage is that the resultant clones are space efficient or pre-deduplicated or non-duplicated clones. This also means that you do not need to provision space in advance, the periodic deduplication jobs are shorter and if you have a DR site then almost no data needs to be replicated to the DR site after you have created new VMs. To understand more about FlexClone and various options around it you can refer the NetApp Technical report here

Some Screenshots from my test environment
My test environment has a FAS2040 with 7 disks connected to 2 x vSphere 5 servers. I have a Windows 2008 R2 template by the name of WIN2K8R2SVR-template, 42GB in size which I used to create my clones. As you can see in the screenshot below, the clone from WIN2K8R2SVR-template to win2k8r2-1 took around 8 minutes (marked with a black arrow). Other two clones, from win2k8r2-1 to win2k8r2-2 and one from win2k8r2-2, which are within the same datastore took around 2.5 minutes each (marked with blue arrows).

Then I used the NetApp Rapid Cloning utility to create 5 new clones which took around 15 minutes to get created.

Best of all is that all these new VMs used only a fraction of space giving me 87% of space savings without even enabling Deduplication. This is where we get the real advantage of sub-LUN cloning.

In case of NFS, NetApp has always had the rapid cloning utility which used the file level cloning to rapidly clone VMs without utilizing any space. Recently we extended it to VMware’s native cloning with VAAI for NFS. With Sub-Lun cloning, we bring the same advantage to the SAN World. Now you can clone individual VMs within a VMFS LUN using either Rapid Cloning Utility or Native VMware cloning which is not only faster but also space efficient.

What do you think of this enhancement?

One thought on “VMware VAAI and Sub-LUN Clones – A hidden gem

  1. Pingback: New in Clustered ONTAP – Improved Single File Restore (Think quick VM level recoveries) | Virtual Data Blocks

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