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SOA's Perfect Mate?: Page 8 of 10

Vordel and Layer 7 both say their virtual appliance editions were aimed initially at testing, yet some customers already use them in production environments. Both vendors expect this trend to grow. Compared with hardware appliances, virtual appliances are easier to install and manage, with server resources dedicated to the VM as required. For example, Layer 7 partner Sun is promoting the concept of on-demand security, in which security services are applied as needed from a virtual appliance.

The theory is that, because Web services are relatively easy to develop, they won't always be built by IT and may run afoul of enterprise security policies. Security gateways provide a way to contain such rogue services without necessarily harming functionality. "You can use the security gateway to buffer a service from its client," says Kevin Schmidt, director for SOA products at Sun. "Virtualizing the gateway becomes an issue of performance and manageability."


The Match Game
All Web services platform vendors have virtualization offerings, though most depend on using the same vendor's OS
VENDOR WEB SERVICES PLATFORM OS SERVER VIRTUALIZATION PRODUCTS
BEA JRockit None (Oracle offers Linux) LiquidVM (Oracle offers Xen)
IBM WebSphere AIX, Linux (Novell, Red Hat) System p, System i, Xen
Microsoft .Net Framework Windows Server Windows Virtual Server, Hyper-V
Red Hat JBoss Red Hat Enterprise Linux Xen
Sun Java System Solaris Containers, xVM (Xen)

FABRICATING APPS

For a truly agile infrastructure, virtualization must enable IT to spread an application across multiple servers, not just split a single server into several VMs. This is an even tougher nut to crack than standard server virtualization, however, because most apps today are fairly linear and can't easily separate their processing into multiple parallel operations. Developers are working to make apps parallel for multicore CPUs, but clustered servers pose additional bandwidth and latency challenges. For example, multiple cores within a single server can communicate with one another quickly and access common memory, but multiple servers in a cluster need to rely on networks, which are much slower.

For this reason, most approaches to clustered Web services don't try to break services into parallel chunks. Instead, application fabrics from vendors like Appistry and DataSynapse install an app on multiple servers and load-balance across them. This works well for most SOA traffic, as Web services usually involve responding to multiple user requests, which can easily be spread across several servers.