18. Comparison of Architectures Wide use of chip-based machine virtualization Limited use of OS-based machine virtualization Machine Virtualization Wide use Limited use Application Virtualization Limited use Limited use Thin Client Limited use Limited use OS Streaming Uses file-based disk imaging technology Uses sector-based disk imaging technology OS Deployment Primarily rich Windows client Today Primarily rich Windows client OS Tomorrow Component/Solution
19.
Editor's Notes
The impact of machine virtualization on desktop computing to date has been limited. Products like Microsoft’s Virtual PC and VMware workstation, although relatively mature and well understood, have not been widely adopted as a general purpose desktop management technology. The primary use case for these products has been by IT professionals who need to create and maintain isolated development and test environments. However, machine virtualization on the desktop has not proven valuable either to the average corporate user or the IT department managing those users. There are a number of general purpose use cases that have been considered. The first is the use of machine virtualization as a general solution desktop deployment and management. However, the main OS deployment benefits of machine virtualization such as image and driver standardization are outweighed by technical costs of running a VM on top of a machines host OS. The technical costs include the need to manage both the host and the guest OS (i.e. service packs, security fixes, etc.), the performance hit and potential device management issues (devices that are not supported inside the VM.) Others have contemplated using virtual machine technology to solve desktop application deployment and management challenges. Using VM’s to solve these issues, however, is very much a sledgehammer approach. Using VM technology to solve application conflict, for example, requires the hosting of multiple OS instances on a user’s desktop which results in reduced performance both within the guest and host environments. Multiple OS instances also create user experience issues because users get confused as to which session they are viewing. Also, applications running within different sessions (whether a guest OS or the host) are running in completely isolated context, which restricts the kind of interaction possible between applications running in the different environments. For these reasons, machine virtualization has not become widely used by standard users in the corporate enterprise. Even solutions like VMware’s ACE, which attempts to centralize some of the management aspects of VM creation and security policy enforcement, have only proven useful for edge cases in the enterprise, such as contract employees using their own devices or stationary remote employees using home PC’s or other unmanaged devices.
All thin client architectures, from traditional Terminal Services-based environments to both dedicated (ClearCube, HP CCI) and virtualized (IBM VHCI, VMware VDI) solutions, suffer from the same core limitations: For users with a fat desktop or laptop computer (which is 90 – 95% of the typical enterprise), deploying a thin client solution involves the provisioning of redundant compute resources in the data center. Data center systems (in the form of Terminal Servers or dedicated/virtualized blades servers are more expensive then client compute resources. Economically, this is becoming harder and harder for the CIO to justify to the CFO, especially as the cost of client devices continues to decline. Thin client architectures suffer from application execution context issues. This is due to the fact that applications executing in the thin client environment are running on a system in the data center; however, the user is running an OS and core applications locally on their machine (assuming a fat desktop or laptop model.) Therefore, the applications running in the thin client environment are not aware of and cannot communicate with those running locally and vice versa. Also, manipulation of data files becomes challenging (especially for non-technical end-users) when an application on the desktop requires a data file that resides in the data center and vice versa. Thin client architectures do not support disconnected or offline operation
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