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The Desktop as a Grid Service
Test-Driving Sun's Prototype Display Grid
by Frank Sommers
February 8, 2006

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Thin Client Grid Computing: Test-Driving Sun's Display Grid

The rest of this article focuses on an implementation of the replicated frame buffer cache paradigm, Sun's Sun Ray[20]. The Sun Ray's architecture is novel in that it pushes almost all computation to the network. Indeed, the Sun Ray client, a small piece of hardware that connects to a keyboard, a mouse, a display, and a network cable, does so little computing that it can operate on about 9W of electricity.

At the heart of the Sun Ray architecture is a communication protocol that relays status between server and client, including information about user authentication and a user's desktop session, sends keyboard and mouse state to the server, forwards audio and peripheral I/O between server and client, and transports screen updates from the server to the thin client. The Sun Ray's local screen buffer is used for display updates, but that cache is treated as ephemeral that can be overridden by the server at any time. Thus, the client is stateless. The firmware in the Sun Ray device contains networking code as well as code specific to the Sun Ray protocol.

CommandDescription
SET Set literal pixel values of a rectangular region
BITMAP Expand a bitmap to fill a rectangular region with a (foreground) color where the bitmap contains 1's, and another (background) color where the bitmap contains 0's
FILL Fill a rectangular region with one pixel value.
COPY Copy a rectangular region of the frame buffer to another location
CSCS Color-space convert a rectangular region from YUV to RGB with optional bilinear scaling
Table 1: A sample of Sun Ray protocol commands

The latest Sun Ray version at the time of writing provides built-in support for DHCP and virtual private networking, and the Sun Ray protocol was updated to work over low-bandwidth networks. The result is that a user can access a Sun Ray server over a wide-area network, such as a broadband residential connection.

Sun has made remotely hosted desktop sessions available to some of its employees as part of the company's work-at-home program for some time. More recently, Sun started to position the Sun Ray as a way to offer consumers a subscription-based desktop service as well. Since the Sun Ray architecture translates desktop management to a highly parallel, grid computing task, Sun's expertise in high-throughput computing puts the company in an advantageous position to offer such a service.

To determine how well such a remotely hosted Sun Ray desktop can supplant a user's traditional desktop computer or laptop, we performed a four-month evaluation of Sun's prototype hosted desktop environment, a proof-of-concept of a broadband desktop service. The Sun Ray desktop used in this evaluation was hosted on Sun's CXONet facility on the US East Coast, and we have accessed that desktop via a residential DSL connection from California. The workload used in this evaluation consisted of four main categories of applications: an email client (Mozilla Thunderbird), a Web browser (Firefox)[21], a word processor and spreadsheet (OpenOffice)[22], and an IDE to work on source code (IntelliJ IDEA)[23].

Using daily the remotely situated desktop for those task instead of a usual desktop or laptop environment caused no loss of productivity. Because those applications were running on fast servers, the system proved remarkably responsive. Based on causal observation, application startup, for instance, tended to be quicker than on a laptop with a 3.2 GHz Pentium 4 CPU.

At the same time, occasional hick-ups in screen redraw operations remind the user of the network's presence between the display and the remote desktop server. As expected, redraw latency was most pronounced when moving windows around the desktop or scrolling documents in a window: It does take a perceptible amount of time for the Sun Ray to catch up and completely redraw the screen. While a user can get used to that redraw latency, broader consumer adoption of the Sun Ray desktop might require further investigation into how such delays can be reduced, if not completely eliminated.

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