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Creating SE Sparse Linked Clones Using the vSphere 5.1 API

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In my previous article, I showed you how you can easily create your own SE Sparse (Space-Efficient) disks for you virtual machines running on vSphere 5.1. In addition to just creating new virtual disks using the new disk format, you can also create SE Sparse Linked Clones by leveraging the vSphere 5.1 API. I had previously shared a vSphere SDK for Perl sample script called vGhettoLinkedClone.pl that allows you to create your own Linked Clones and I have updated the script to now support the new SE Sparse disk format.

The script now includes new parameter called --convert which allows you to specify whether or not the destination Linked Clone should follow the same source virtual disk format or the new SE Sparse disk format. Remember to upgrade your VMs to the latest ESXi 5.1 compatibility and later (virtual hardware version 9) if you wish to leverage the new SE Sparse disk format. The way this is accomplished is by specifying a new disk backing  VirtualDiskFlatVer2BackingInfo in the VirtualMachineRelocateSpec and passing in the deltaDiskFormat to be of type seSparseFormat.

Disclaimer: This is for educational purposes only, this is not officially supported by VMware. Please test this in a development environment before using it on actual systems.

Note: Linked Clones is a feature of vCenter Server, make sure you are connecting to a vCenter Server 5.1

If you have a VM that has a VMDK that is NOT an SE Sparse disk format but wish to create Linked Clones with the new SE Sparse disk format, then you can use the --convert sesparse option, here is an example command:

./vGhettoLinkedClone.pl --server vcenter51-1.primp-industries.com --username root --vmname Regular-VM --vmname_destination Linkedclone-SeSparse-Destination --snapname pristine --vmhost vesxi51-1.primp-industries.com --datastore datastore1 --convert sesparse

If you have a VM that has a VMDK that IS an SE Sparse disk format and you wish to create Linked Clones with the same disk format, then you can use the --convert source option, here is an example command:

./vGhettoLinkedClone.pl --server vcenter51-1.primp-industries.com --username root --vmname SeSparse-VM --vmname_destination Linkedclone-SeSparse-Destination --snapname pristine --vmhost vesxi51-1.primp-industries.com --datastore datastore1 --convert source

If we head over to our vSphere Web Client and take a look at our new Linked Clones, we can confirm their virtual disks is using the new SE Sparse disk format.

How to Create an SE Sparse (Space-Efficient) Disk in vSphere 5.1

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You probably may have heard, that with the upcoming release of vSphere 5.1, a new virtual machine disk format will be introduced called called SE Sparse (Space-Efficient). One of it's features is to provide the ability to reclaim unused blocks from within the guestOS. I would highly recommend you check out a recent blog post vSphere 5.1 Storage Enhancements – Part 2: SE Sparse Disks by Cormac Hogan for more details about the new SE Sparse disk format as well as other storage improvements in vSphere 5.1.

As Cormac points out, this new disk format will initially be leveraged by VMware View (in a future release from my understanding), as there are additional integrations required to use this feature than just using the new SE Sparse disk format. Having said that, the SE Sparse disk format is a feature of the vSphere 5.1 platform and with that, you do have the ability to create an SE Sparse disk.

Disclaimer: This is for educational purposes only, this is not officially supported by VMware. Please test this in a development environment before using it on actual systems.

There are two methods in which you can create an SE Sparse disk, directly on the ESXi Shell of an ESXi 5.1 host or remotely connecting to an ESXi 5.1 host.

Option 1 - Using vmkfstools on ESXi Shell 

Though it may not be documented, you can easily create a new VMDK with the new SE Sparse disk format by running the following command (10GB disk in this example):

vmkfstools -c 10g -d sesparse WindowsXP.vmdk

Here is a screenshot of new SE Sparse disk descriptor file to prove we have successfully created a new VMDK using the new format:

Option 2 - Using vSphere 5.1 API w/modified remote version of vmkfstools

As mentioned, the SE Sparse disk format is a feature of the vSphere 5.1 platform and as so, you can also leverage the vSphere 5.1 API to create a new VMDK using the virtualDiskManager and specifying the new SeSparseVirtualDiskSpec.

Note: Even though the vSphere API reference mentions the ability to set grain size via grainSizeKb property, I have found that it is not possible and just leaving it blank will automatically default to 1024K (1MB) which might be a system default for now.

You can download the modified version of the remote vmkfstools called vmkfstools-lamw which requires the the installation of vCLI 5.1 or vMA 5.1.

Here is an example of creating the same 10GB VMDK using the new SE Sparse disk format:

./vmkfstools-lamw --server 172.30.0.187 --username root -c 10G -d sesparse "[datastore1] WindowsXP.vmdk"

After you have created your new SE Sparse disk, the next logical step is assign it to a virtual machine. Since this is a new feature in vSphere 5.1, you will need to use the new vSphere Web Client to perform the operation as the legacy vSphere C# Client is not aware of this new disk type. You will also need to ensure that the virtual machine is running the latest ESXi 5.1 compatibility and later (virtual hardware version 9).

Once you have added our newly created disk from the datastore, it should now show up in the vSphere Web Client as Flex-SE for the disk type.

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Auditing vMotion Migrations

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I saw an interesting question this week about auditing vMotion events and the number of times a VM has migrated to a particular ESX(i) host for license compliance. You can view this information using the Task/Events in your vCenter Server but you can also extract out the various types of events using the EventManager in the vSphere API. You will be able to go as far back in time as your vCenter Server's database retention policy allows you to. We will be searching for the VmMigratedEvent Event which will include variety of information including the source and destination host for the VM. The destination host will only be populated upon a successful vMotion.

Of course I had to write a script to help automate this, so here is a vSphere SDK for Perl script called getNumberOfvMotions.pl that accepts the name of an existing VM and will return the number of vMotions that has been performed on the VM as well as the list of destination hosts and the number of times it has migrated to those hosts. You will need a system that has the vCLI installed or you can you use vMA.

Note:  If you want to look at past vMotion for a VM that no longer exists, this is still possible, but you will need to parse the "message" within the Event as you can no longer look up that VM object in vCenter.

Here is an example of the script running:

You can easily modify the script to audit all VM's in your environment or just use a simple "for" loop to go through a set of VM's you are interested in, but I will leave that as an exercise for you.