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Upgrading from VMware Server to ESX 3.5: The pros and cons

Upgrade from VMware Server to ESX 3.5, and you'll get more functionality, flexibility, better management tools and extended data center control. But you'll face problems if you implement IDE and dynamic disks.

This tip teaches you the pros and cons of migrating from the free VMware Server to the more costly but more enterprise-ready products, VMware ESX 3.5, VMware Infrastructure 3 and the VMware Infrastructure Suite.

David Davis

Few tutorials cover the process of planning the move, and moving, from VMware Server 1.x to VMware ESX Server 3.x or 3.5 and the VMware Infrastructure (VI) Suite. In this series on planning and performing this migration, I cover every aspect of doing this job properly.

The few VMware Server to ESX 3.x or 3.5 tutorials available only cover how to migrate a single machine from VMware Server to ESX Server. While that's still important, system administrators need to know more about the mass migration of servers from VMware Server to VMware ESX, rather than migrating a single server.

In the first part of this series, I explain when and why a company should migrate from VMware Server to ESX and VI. My next piece describes four steps for successfully completing this important conversion, another step in guiding you in your virtualization conversion.

VMware Server to ESX and VI: A common scenario

I would be willing to bet that most VMware ESX Server users out there didn't start using ESX to being with. Most users started with either VMware Server 1.x or Microsoft Virtual Server. Those mid-grade virtualization products aren't just for smaller IT shops. These products are the logical and conservative place to start your virtualization project.

Because these two products are free and they don't require anything more to run than a typical PC, they make the ideal virtualization entry point for desktop virtualization users, test/evaluation virtualization projects, and, of course, production virtualization environments.

VMware Server production virtualization environments could be a single server, or they could be dozens of servers with Virtual Center for VMware Server centralized management software.

However, at some point in a production virtualization environment, the debate to move to the products with better performance and more features, namely VMware ESX Server and the VMware Infrastructure Suite – will come up.

When you get to that point, what do you do? What is the plan? What needs to be considered? How will you make that move without causing downtime for the end users and creating as little end user distribution as possible? Let's find out.

Why make the move from VMware Server to ESX Server and the VI Suite?

There are many reasons to move from VMware Server to ESX Server. If you are reading this then you probably already have some interest in VMware ESX Server. But what is the justification? Let's look at some reasons:

  • Performance – ESX Server offer greater performance than VMware Server because ESX runs directly on the hardware. Because of this, there is no overhead from the host operating system.


  • Functionality – With ESX and the VMware Infrastructure Suite, you get features like VMotion, VCB, DRS, and VMware High Availability. These products aren't found in any free virtualization product.


  • Improved management and flexibility – With the VirtualCenter centralized console you can gain control over all locations, virtual servers, features, performance, security and availability, all in one place. While there is the option of using the VMware Server Console for VMware Server, that application still won't provide the functionality of VMware's VirtualCenter.


  • Increased data center control – With Virtual Center's centralized management, you can control ESX Servers, not just at your location, but at all servers across all locations, from a single point.

Upgrading from VMware Server to ESX Server: Cons

While VMware Server and VMware ESX Server are both VMware Server products, there are still a couple of pitfalls you need to be careful to avoid when planning and performing your migration to ESX Server.

  • IDE versus SCSI virtual disks – VMware Workstation and Server both support IDE and SCSI disks as the disk type for any new virtual disks. However, when you move to ESX Server, you will find that IDE disks are not supported. To resolve this, you need to convert all IDE virtual disks to SCSI disk. The easiest way to do this is to use a tool like VMware Converter that will change the disk type and driver during the conversion.


  • Dynamic versus fixed virtual disks – VMware Server supports dynamic disks that can grow as the data inside the virtual disk grows. These help save space and prevent you from having to resize your disk later. While they are a nice feature, they aren't good for performance because they become fragmented over time. VMware ESX doesn't support these dynamic disks. Thus, if your VMware Server virtual machines have dynamic disks, you will have to convert these to fixed disks during the conversion process. However, be careful as say that you have a 500 GB dynamic disk in VMware Server but you only have 3 GB of it used, some conversion applications will create a fixed disk that is the same size (but mostly empty) after the conversion.


In conclusion, converting from VMware Server to VMware ESX Server is a logical progression for any company. If you can justify the expense to your company, VMware ESX Server is certainly a much more robust virtualization product. While there is documentation on how to migrate individual virtual machines to ESX Server, there aren't a lot of documents that cover the planning and implementation of such a move. In part two of this series, I describe how to analyze and document this important conversion to guide you in your virtualization conversion. I hope you will take a look!

David Davis has served as an IT Manager for over 15 years. He has a number of certifications including CCIE #9369, MCSE, CISSP, and VCP. Additionally, David has authored over one hundred articles, a number of video training courses, some of which are available at his Web site, HappyRouter.com.

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