BEA WebLogic VE brings virtualization to the application server

As IT finds itself slowly but irresistibly sucked into the virtualization phenomenon, vendors of application servers have begun to participate in the new trend. Perhaps the most aggressive and innovative of these vendors has been BEA, a company that has always prided itself on being an early adopter of new standards and technologies.

Several years ago, BEA began research into the feasibility and benefits of running its JRockit Java VM directly on the virtualization platform, or hypervisor, rather than relying on intermediate operating systems. At the time, this effort was intended as a performance boost. By eliminating the operating system, the Java VM could communicate directly with the server VM about key activities such as thread scheduling. The version of JRockit that resulted from this research was called BEA LiquidVM, and although it was not released as a separate product by BEA, it forms the basis of a virtualized appliance that runs the company’s flagship WebLogic application server. This appliance, known as BEA WebLogic Server Virtual Edition (VE), delivers interesting innovation, but awaits the arrival of a central management system before it is ready for deployment in production environments.

Inside the appliance

The concept of virtual appliances might need some explanation. Appliances consist of a stack of software that runs on top of a virtual machine. What makes it an appliance is that the layers of the stack have been wired together beforehand and properly configured so that users simply install the stack as a single product and use it without additional configuration. It’s a turnkey implementation. VMware, the market leader in virtualization, offers an online directory of virtual appliances. Many of the entries there are free, as they capitalize on the wealth of open source software to create useful stacks. For example, you can find an appliance called OpenBSD MailServer, which integrates the OpenBSD operating system, a mail server, a spam filtering package, and a Web server interface, all preconfigured and ready to run. The virtual appliance model will surely become more common in IT; in fact, I expect it will soon be the default delivery vehicle for packages. BEA might well be the vendor that first familiarizes IT sites with this approach.

The VE appliance includes the WebLogic 9.2 Server Premium Edition, the LiquidVM, and a thin interface shim that operates between the JVM and the VM. In this case, the VM must run on VMware ESX Server. (Demo versions are available for VMware Workstation.) The shim layer between the JVM and the VM is where the magic occurs — it’s the stand-in for what is usually the operating system layer. And while it replaces key functions, it does not include a file system — that is, not one that is accessible by the layers above the JVM. Consequently, all files used by the app server must reside on a remote device, such as a NAS or SAN.

This design means that disk I/O will be somewhat slower than if the accessed files were local to the app server. However, it provides a crucial advantage: The appliance remains fairly small in size and is easily migrated from system to system. This last point is central to understanding the value of the product, as I explain in the next section.