Next: Introduction

# A Hierarchical Internet Object Cache

Anawat Chankhunthod
Peter B. Danzig
Chuck Neerdaels
Computer Science Department
University of Southern California
Michael F. Schwartz
Kurt J. Worrell
Computer Science Department
University of Colorado - Boulder

### Abstract:

This paper discusses the design and performance of a hierarchical proxy-cache designed to make Internet information systems scale better. The design was motivated by our earlier trace-driven simulation study of Internet traffic. We challenge the conventional wisdom that the benefits of hierarchical file caching do not merit the costs, and believe the issue merits reconsideration in the Internet environment.

The cache implementation supports a highly concurrent stream of requests. We present performance measurements that show that our cache outperforms other popular Internet cache implementations by an order of magnitude under concurrent load. These measurements indicate that hierarchy does not measurably increase access latency. Our software can also be configured as a Web-server accelerator; we present data that our httpd-accelerator is ten times faster than Netscape's Netsite and NCSA 1.4 servers.

Finally, we relate our experience fitting the cache into the increasingly complex and operational world of Internet information systems, including issues related to security, transparency to cache-unaware clients, and the role of file systems in support of ubiquitous wide-area information systems.

SPARC-center

- Introduction
  - Hierarchical Web versus File System Caches
- Design
  - Cache Hierarchy
  - Cache Access Protocols
  - Cacheable Objects
  - Unique Object Naming
  - Negative Caching
  - Cache-Awareness
  - Security, Privacy, and Proxy-Caching
  - Threading
  - Memory Management
  - Disk Management
- Performance
  - Harvest vs. CERN Cache
  - Httpd-Accelerator
  - Httpd-Accelerator vs. Netsite &NCSA 1.4
  - Decomposing Cache Performance
  - Cache Hierarchy vs. Latency
- Cache Consistency
  - Object Lifetimes
  - Hierarchical Invalidation
- Experience
  - Transparency
  - Deployment
  - Open Systems vs. File Systems
- Related Efforts
- Summary
  - Software and Measurement Data Availability
  - Acknowledgments
- References
- About this document ...