2/18/2004 Challenges in Building Internet Services February 18, 2004

2/18/2004 Assignments Due – Project 1 Start work on Registrar Assignment

2/18/2004 Design Goals Fast service (low latency) Service all users (scalability) Always available (fault tolerance)

2/18/2004 A Registration Website Fast service –Assume users on campus Service all users –Only need to service MHC students Always available –Can tolerate some failure

2/18/2004 Pieces of the Puzzle Load Balancing Servers Data Store

2/18/2004 Design Goals Fast service (low latency) Service all users (scalability) Always available (fault tolerance) How does the picture change?

2/18/2004 Pieces of the Puzzle Servers Data Store

2/18/2004 Issues How does my client choose a server? Do all servers do the same thing? Do all data stores have the same information?

2/18/2004 Pieces of the Puzzle Load Balancing Servers Data Store

2/18/2004 Issues How does my client choose a server? –Transparency –Maintaining client state –Geographic location

2/18/2004 Issues Do all servers do the same thing? – Do all data stores have the same information? –Replication –Partitioning

2/18/2004 Issues Do all servers do the same thing? – Do all data stores have the same information? –Replication Consistency –Partitioning Finding correct server/data store

2/18/2004 Fault Handling What happens if a server/data store fails?