Distributed Systems Lecture #2 URL:

Operating System Securely and efficiently multiplex hardware –Abstraction Memory Processor (clock) Peripherals –Communication

Single Processor OS Memory P1P2 Processor OS Kernel Process management Memory management IPC -- Naming, Concur Storage

Distributed OS Memory P1P2 Processor OS Kernel Process management Memory management IPC -- Naming, Concur Storage Processor Memory

Issues Same but different: Distributed P1P2 Network Delay Lossy

Big Debate Hide or expose? –Distributed OS: Hide –Middleware: Expose Resource Management Communication –How: Naming!!

Why Distribute? To access resources Improve availability Enhance fault-tolerance Consider Yahoo Mail vs. Airline Ticketing System

Yahoo Mail Millions of users Quite a heck lot of data Do all on one machine? Distribute? –Performance? Distributed Load –Reliability? Replicate Data –Scalability? –Security

Airline Ticketing System Distribution not exactly by choice –Consistency? –Performance? –Reliability? –Scalability?

Illegal MP3 Sharing Loosely coupled Scalable? Consistent? Highly Available? Secure?