1.  What is Grid Computing?

Computational Grid  is a collection of distributed, possibly heterogeneous resources which can be used as an ensemble to execute large-scale applications

• Computational Grid also called metacomputer

• Term computational grid  comes from an analogy with the electric power grid:
• Electric power is ubiquitous
• Don't need to know the source (transformer, generator) of the power or the power company that serves it

• In the box parallel computers, as evidenced by the PetaFLOPS initiative
• Increasing development of infrastructure and middleware to leverage the performance potential of distributed Computational Grids

Distributed Supercomputing

• Distributed Supercomputing applications couple multiple computational resources - supercomputers and/or workstations

• Distributed supercomputing applications include SFExpress (large-scale modeling of battle entities with complex interactive behavior for distrtibuted interactive simulation), Climate Modeling (modeling of climate behavior using complex models and long time-scales)

• Grid used to schedule large numbers of independent or loosely coupled tasks with the goal of putting unused cycles to work

• High-throughput applications include RSA keycracking, seti@home (detection of extra-terrestrial communication)

• Focus is on synthesizing new information from large amounts of physically distributed data

• Examples include NILE (distributed system for high energy physics experiments using data from CLEO), SAR/SRB applications, digital library applications

Gigabit Testbeds Program

• Late 80's, early 90's, gigabit testbed program was developed as joint NSF, DARPA, CNRI (Corporation for Networking Research, Bob Kahn) initiative
• Idea was to investigate potential architecture for a gigabit/sec network testbed and to explore usefulness for end-users
• 5 testbeds formed: CASA (southwest), MAGIC and BLANCA (Midwest), AURORA and NECTAR (northeast), VISTANET (southeast), each had a unique blend of research in applications and in networking and computer science research:

I-Way

• First large-scale Grid experiment
• Put together for SC'95
• I-Way consisted of a Grid of 17 sites connected by vBNS
• Over 60 applications ran on the I-WAY during SC?95
• Each I-WAY site served by an I-POP (I-WAY Point of Presence) used for authentication of distributed applications, distribution of associated libraries and other software, and monitoring the connectivity of the I-WAY virtual network
• Users could use single authentication and job submission across multiple sites or they could work directly with end-users
• Scheduling done with a human-in-the-loop

• 2 NSF Supercomputer Centers (PACIs) - SDSC/NPACI and NCSA/Alliance, both committed to Grid computing although the effort has been stronger at NCSA
• vBNS backbone between NCSA and SDSC running at OC-12 with connectivity to over 100 locations at speeds ranging from 45 Mb/s to 155 Mb/s or more
• Applications include data-intensive computing (NPACI), visual supercomputing and teleimmersion (Alliance).
• Access Grid by NCSA serves to connect sites for collaboration work in distributed environments and group interactions

• Globus testbed = GUSTO which supports Globus infrastructure and application development
• Centurion Cluster at UVA = Legion testbed
• IPG = supported by NASA as grid computing testbed, Globus is supported as infrastructure and application and middleware development efforts are underway

Cluster computing focuses on platforms consisting of often homogeneous interconnected nodes in a single administrative domain.

• Clusters often consist of PCs or workstations and relatively fast networks
• Cluster components can be shared or dedicated
• Application focus is on cycle-stealing computations, high-throughput computations, distributed computations

• Web consists of very diverse set of computational, storage, communication, and other resources shared by an immense number of users
• Application focus is on access to information, electronic commerce, etc.

• Some grid resources may be shared, other may be dedicated or reserved
• Application focus is on high-performance, resource-intensive applications

Legion and Globus are the two best-known infrastructure efforts.

Globus -  integrated toolkit of Grid services.

• Developed by Ian Foster (ANL/UC) and Carl Kesselman (USC/ISI)
• Bag of services   model - applications can use Grid services without having to adopt a particular programming model
• Globus services include :
•  Resource allocation and process management (GRAM)
•  Communication services (Nexus)
•  Distributed access to structure and state information (MDS)
•  Authentication and security services (GSI)
•  System monitoring (HBM)
•  Remote data access (GASS)
•  Construction, caching and location of executables (GEM)

• Provides single, coherent virtual machine model that addresses grid issues within a reflective, object-based metasystem
• Everything is an object in Legion model - HW resources, SW resources, etc.
• Every Legion object is defined and managed by its class object; class objects act as managers and make policy, as well as define instances
• Legion defines the interface and basic functionality of a set of core object types which support basic services
•  Users may also define and build their own class objects