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FAQ: Virtual machine migration to vSphere

Use this FAQ to get advice for performing a virtual machine migration from Hyper-V or XenServer to vSphere and learn about incompatibilities among hypervisors.

Before performing a virtual machine migration from Hyper-V or XenServer to vSphere, solutions providers need to take many factors into consideration. Virtual machine migration is a challenging process that can be riddled with incompatibility issues.

Virtualization expert Eric Siebert explains that before starting the virtual machine migration process, you need to be aware of potential setbacks, including problems with different virtual disk file formats and a lack of standards. Find out the proper way to format virtual machines (VMs) and virtual disk files and learn why there isn't an industry-standard VM file format.

 

Read Eric Siebert's answers to other frequently asked questions on virtual machine migration tools.

Listen to the podcast here.
 

FAQ: Virtual machine migration to vSphere

Right-click on the podcast link to download the file as an MP3!

Read a transcribed version of the podcast or get more resources.

 

How difficult is a virtual machine migration from Microsoft Hyper-V or Citrix XenServer to VMware vSphere?
Before performing a virtual machine migration, what incompatibilities should solutions providers be aware of?
How do virtual disk files differ among the hypervisors?
Is there a vendor-independent standard for VMs that solutions providers can refer to before performing a virtual machine migration?
More resources on virtual machine migration and vSphere virtual machines
About the expert

 

How difficult is a virtual machine migration from Microsoft Hyper-V or Citrix XenServer to VMware vSphere?

Virtual machines are encapsulated into a virtual disk file and several small companion files (i.e., BIOS, configuration), which makes for easy portability. However, migrating Hyper-V or XenServer VMs to vSphere is not as simple as copying those files to a vSphere server and powering on the VM. Because of incompatibilities among vSphere VMs and Hyper-V and XenServer VMs, you must first convert VMs to the format used by vSphere. Fortunately, a number of vSphere virtual machine migration tools exist to make this process fairly straightforward and easy.

 

Before performing a virtual machine migration, what incompatibilities should solutions providers be aware of?

The biggest incompatibility between Hyper-V, XenServer and vSphere is the virtual disk file, which uses different proprietary formats. Configuration files, which are text files that contain the settings and virtual hardware information for the VM, are also proprietary. VSphere uses .vmx files, and Hyper-V and XenServer use .xml files. In addition, there are other files such as BIOS and snapshots that have proprietary file formats. These different file formats make conversion necessary when going from one hypervisor to another.

 

How do virtual disk files differ among the hypervisors?

VMware uses a proprietary Virtual Machine Disk (VMDK) format that it developed, and XenServer and Hyper-V use a proprietary Virtual Hard Disk (VHD) format. These formats are completely different from each other and cannot be used directly with another hypervisor. When performing a virtual machine migration, there are a number of tools and utilities that will convert virtual disks from one hypervisor format to another.

 

Is there a vendor-independent standard for VMs that solutions providers can refer to before performing a virtual machine migration?

Because each vendor is competing with one another, there has not been a strong push to have a universal format that all hypervisors can use. An Open Virtualization Format (OVF) was proposed by all of the leading vendors but was more a universal method of packaging and distributing VMs than an actual virtual machine file standard. The OVF uses .xml files to describe the configuration of a VM and is not specific to virtual disks, which remain proprietary to each specific vendor. Today, the OVF is mainly used for importing and exporting VMs to any of the hypervisors that support it.

 

More resources on virtual machine migration and vSphere virtual machines:

Four rules for virtual machine migration

Virtualization best practices to accelerate virtual machine migration

Creating a virtual machine and VM configuration in VMware vSphere

VMware virtual machines in vSphere: Options and hardware

Xen vs. KVM and KVM migration guide

 

 

About the expert
Eric Siebert is a 25-year IT veteran whose primary focus is VMware virtualization and Windows server administration. He is one of the 300 vExperts named by VMware for 2009. He is the author of the book
VI3 Implementation and Administration and a frequent TechTarget contributor. In addition, he maintains vSphere-land.com, a VMware information site.

This was last published in March 2010

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