Predictable Computer Systems

Remzi Arpaci-DusseauUniversity of Wisconsin,

Madison

Trends

Trends

Complexity

Cheap Components

Everything Interconnected

Problems

Nothing Works As Expected

Performance

Fault-Tolerance

Security

What Would Be Ideal

Ideal

Assemble large-scale systemfrom 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 Behaviorof 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

failuresat different points in its code

Write Errors: Recovery Techniques

Ext3, JFS don’treact to write failures

ReiserFS (almost) always calls panic()

Zero

Stop

Propagate

Retry

Redundancy

Reco

very

Ext3 ReiserFS JFS

What We Need

What We Need

Vocabulary

+Techniqu

es +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-DusseauRemzi 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 StorageArchivalStorage

Internet

Clients

Ideal: Legos

Top Side

What You See Is What You Get