Various Scenarios addressing ‘Virtualization’ technologies:
Scenario 1: HW Virtualization: This scenario would include technologies such as Solaris Zones and Logical Partitioning (LPARs) on AIX5L. The platforms address the needs of a growing data centers and bring forward the efficient use of consolidated and powerful hardware resources. The core principle offered by these technologies are resizing based on capacity. While these technology have largely addressed the growing needs of a data center by efficiently managing power, space and hence the costs, at the core of its value proposition leis the appeal of business continuity. The system (HW) resources such as a RAM, CPU, Network IO etc can be easily added or removed from a logically defined partition, based on capacity, without any interruptions such as system restarts ( reboot due to resource constraints). Hence by providing this level of virtualization at the HW levels the higher level applications (any application), unaware of lower level dynamic resource allocation can operate, and use resources provided by the Operating system.
Scenario 2: Runtime Virtualization: This is enabled by products such as VMware. VMware which virtualizes the runtime essentially allows of portability and ease of management (with factory like deployments). So while ‘virtual runtime’ does not provide any resource pooling and optimization features, it can be very instrumental in scenarios that require fast turnaround times such as a product demos, lab environments etc. This ‘rip-n-replace’ appeal of VMware products has also found place in large enterprise deployments, essentially to keep support costs in check. By virtualizing runtime, the virtualized images can run anywhere in the infrastructure on any HW/SW platform, since the virtual runtime is defined and is usually consistent across enterprise.
Note: With release of technologies such as VMware ESXserver, we have seen developments and offering by VMware that is creeping into areas of virtualizing the hardware resource pools (as discussed above in scenario 1).
Scenario 3: WebSphere WVE - enabled Virtualization: WebSphere VE on the other hand play a role only in virtualizing the Application runtime environment. So in theory it acts and play above the HW and VMware virtualization level and allows for the user to have a policy driven approach to 'sense and respond' type of management capability. The key factors that separate WebSphere VE from other types of virtualization are, resources allocation based on goals oriented and business policy driven workloads. WebSphere VE enables an infrastructure that accommodates traditional J2EE/JEE type transactional requests and non traditional Java batch/ long running applications. The virtualizes resource pool enabled by WebSphere VE is primarily used drive business activity and prioritize resource allocation to activities of higher economic value to the business. This model differs from the above mentioned scenarios where in sceanrio1 the HW virtualization is blind of types of applications running, and in scenario 2 only the ‘runtime’ is virtualized to maximize on HW investments along with curbing support costs.
Note: So, while there may be overlapping use of term 'virtualization' the value adds differs significantly. In an environment that has virtualized HW platform, it is safe to say WebSphere virtual enterprise (WVE) will play well, since it will only have visibility to resources available to it (provided by defined allocation policy).