The Globus Consortium Journal recently had the opportunity to catch up with Raj Kumar and Xiang Song from HP's research labs. They're working on an effort called "GridLite" (click here to check out an overview on their project) -- a proof of concept Grid project that's exploring the boundaries of what it means for "lite" mobile devices to participate in a Grid. Mobile devices have legitimate resource constraints (limited storage, memory, compute cycles and so forth) that preclude them from participating in Grids, so it's a tricky problem these guys are trying to solve.

"But if businesses can access the Grid from a laptop or desktop -- they should also be able to access the Grid from a PDA, smartphone or other handheld device," said Kumar.

What Kumar's team has figured out over the last year-and-a-half is a new set of "smart helper" services (sitting above core services) that enable mobile devices to tap into the Grid infrastructure.

In the GridLite architecture, the clients (which include any ubiquitous device like iPaqs or cell phones) contact the server through a portal called GridLite Resource Manager (GRM). If the mobile user is working on an application, the data is brought to the user device, with a master copy kept in the Grid infrastructure. If the user needs to free up some storage on the device, they can flush some extra files to the Grid infrastructure in a seamless fashion. There is a policy engine that allows for thresholds where data moves back and forth from the Grid to the handheld devices, all based on the user's prompting. Predictive algorithms anticipate use of applications (based on recurring usage patterns) and potentially download applications on devices before the user request even occurs.

A big part of what GridLite is addressing is essentially providing an abstraction mechanism that gives the illusion of unlimited storage on the client (mobile device) side. One of the ongoing discussions / debates in Grid -- of course -- is where the intelligence should reside and where the compute should take place. When you're talking about "lite" clients (with the resource constraints mentioned above), the ultimate goal is to make data and storage resources appear local to the user, and to remove any latency or performance issues.

GridLite uses WSRF and WSDM interfaces to web services. The project is also experimenting with a thin client version of the Globus Toolkit.

"We look at the Globus Toolkit as the prefered open source standard for the Grid community," said Kumar. "It uses web services and the standard protocols that give the new services we're developing true interoperability capabilities."

In the GridLite test bed, HP is using GT4's Java web service core as a container, or engine, for running WSRF-compliant web services. That software is about 45 megabytes' worth of code, which is excessive for a handheld - but the GridLite team managed to reduce the GT4 footprint from its 45 megabytes of code down to a 3 megabyte version on the client side.

"The Globus Toolkit has its its own libraries which support both the client and server side," said Song. "For GridLite, on the client (iPaq) side - we don't need all of those libraries. From our point of view, we don't actually need the server functionalities. We don't want the client to do the heavy lifting on the jobs. So we removed some of the libraries from GT4 and only have the required libraries on what you could call a 'thin' client. That client can then submit jobs to servers that can process them much more efficiently."

The GridLite pilot currently operates over wireless LAN - 802.11g. There has been some early exploratory efforts on using GPRS, but currently the emphasis is on WiFi.

So will lessons learned from pilot projects like GridLite have any bearing on how handheld devices are created in the future? Will we see less CPU and storage on the devices - with more of a thin client model, serving up jobs to a Grid infrastructure?

"There are two ways to look at it," said Kumar. "Either you can say that you need less powerful resources on the client side ... or you can say that given the ability to tap into more resources, you can now run more powerful applications on handhelds."

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