Predictable Computer Systems Remzi Arpaci-Dusseau University of Wisconsin, Madison

Trends

Complexity Cheap Components Everything Interconnected

Problems

Nothing Works As Expected Performance Fault-Tolerance Security

What Would Be Ideal

Ideal Assemble large-scale system from cheap, complex components System works in predictable manner

Key: How Components Interact

State of the Art APIs Protocols

Beyond APIs and Protocols: Understanding “Behavior”

A Small Example: Understanding the Failure Behavior of Local File Systems

Understanding FS Failure Type-aware fault injection Make fault injection layer aware of FS structures e.g., make an inode block fail Why useful Can infer how file system reacts to failures at different points in its code

Write Errors: Recovery Techniques Ext3, JFS don’t react to write failures ReiserFS (almost) always calls panic() Zero Stop Propagate Retry Redundancy Recovery Ext3ReiserFSJFS

What We Need

Vocabulary + Techniques + Tools Methods to = Understand Behavior Predictable -> Computer Systems

CSI: Computer Systems Investigation

ADvanced Systems Lab (ADSL) Gray-box Operating Systems and Storage Systems Andrea Arpaci-Dusseau Remzi Arpaci-Dusseau

ADvanced Systems Lab (ADSL) Who does the real work: Nitin Agrawal Lakshmi Bairavasundaram John Bent Nathan Burnett Tim Denehy Camille Fournier Haryadi Gunawi Todd Jones James Nugent Ina Popovici Vijayan Prabhakaran Muthian Sivathanu Who does the real work: Nitin Agrawal Lakshmi Bairavasundaram John Bent Nathan Burnett Tim Denehy Camille Fournier Haryadi Gunawi Todd Jones James Nugent Ina Popovici Vijayan Prabhakaran Muthian Sivathanu

Goal: Building Distributed Systems

Large-Scale Distributed Systems D D W W W Front Ends C C C DBMS Net Online StorageArchival Storage Internet Clients

Ideal: Legos Top Side What You See Is What You Get