Almost everyone will need to convert a physical server to a virtual machine as part of their virtualization deployment. Luckily VMware has provided users with a free tool to help get this done: VMware Converter. There are other physical-to-virtual (P2V) products available, many of which provide more powerful features, more supported operating systems and better performance, but Converter is free and does a pretty good job as well.
VMware Converter combines the functions of VMware's P2V Assistant and Virtual Machine Importer products into one application. It supports both P2V and virtual-to-virtual (V2V) migrations but does not support virtual-to-physical (V2P) (perhaps once you go virtual, VMware doesn't want you going back). There are some methods and products available to do a V2P conversion, but that is beyond the scope of this article.
VMware Converter Standard vs. Enterprise
Converter 3.0 is a standalone product and comes in two versions, the free version (Standard) and the Enterprise version, which is available if you own VirtualCenter. The Enterprise version adds the ability to clone a server remotely (with Standard you have to install it on the server you want to convert), a Boot ISO for cold-cloning a server (with Standard you can only hot-clone), and the ability to perform multiple simultaneous conversions.
Interestingly, the Standard and Enterprise versions are not different applications. You simply download the application, install it and enter a license key to unlock the Enterprise features. Without the license key you are using the Standard version. However, the cold-clone ISO is a separate download only available to licensed Enterprise users. With the release of VirtualCenter 2.5, VMware has integrated Converter directly into VirtualCenter as a plug-in that must be installed and enabled. Also provided with 2.5 are the Boot ISO and a new command line interface (CLI) application that supports both Windows and Linux servers.
Supported software add-ons
Converter works best to convert Windows servers. It supports NT 4.0 (SP6a), XP, 2000, 2003, Vista
Hot and cold cloning
There are two methods used to clone a server, hot cloning (while the server OS is running) or cold cloning (from a boot CD (Windows PE) while the server's OS is not running). Which method you choose will depend on the type of server you are converting. Cold cloning offers the best chance of success because the server OS is not running which will ensure that no data is corrupted since there are no open files while the conversion process is running. This is the best option for data sensitive servers like database and email servers.
Hot cloning works well for less sensitive servers that have more static content like web, print, DNS and application servers. Hot cloning works by creating a snapshot at the beginning of the cloning process and then copying that snapshot to the newly create VM. Any files that are open at the time of the snapshot may not have their data committed which will result in a crash-consistent state for your destination VM. Any subsequent changes to any files after the snapshot is taken will not be copied as well. The snapshot basically creates a point-in-time reference and tracks any block-level changes to the files in the file system. The cloning process uses the snapshot and the files to assemble a reasonable picture of what the entire disk looked like.
Servers to avoid when using Converter
There are certain types of servers that you may not want to use Converter with. Active Directory domain controllers, database and email servers are not good conversion candidates and can experience issues after being converted. If you must convert these type of servers cold-cloning is your best option, if you do choose to hot clone these servers you must make sure the applications are shutdown during the clone process or you will likely end up with corrupted data on the destination VM. Active Directory servers in multiple DC environments are particularly sensitive to USN rollback issues and also possible corruption of AD objects. It's safer and just as easy to create a new VM, install the OS and use dcpromo to make it a DC and then shutdown the old physical server once the new VM is integrated into your domain. Similarly, creating a new VM, installing SQL server, then backing up your databases and restoring them to the new VM is safer then trying to convert a database server.
In our next article in this series we will go into the essential preparation steps necessary to ensure a successful conversion and also the process of running the conversion wizard.
ABOUT THE AUTHOR: Eric Siebert is a 25-year IT veteran with experience in programming,
networking, telecom and systems administration. He is a guru-status moderator on the VMware community VMTN
forums and maintains VMware-land.com, a
VI3 information site.
This was first published in March 2008