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Public Caching

Public Caching. Michael Albrecht Rory Carmichael. Motivation. Distributed filesystems are useful in a variety of circumstances Active Storage Co-locality of some files important Two big problems encountered Network Latency Resource Contention. Potential Solutions. Whole-File Caching

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Public Caching

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  1. Public Caching Michael Albrecht Rory Carmichael

  2. Motivation • Distributed filesystems are useful in a variety of circumstances • Active Storage • Co-locality of some files important • Two big problems encountered • Network Latency • Resource Contention

  3. Potential Solutions • Whole-File Caching • Copies only help one person/machine • Replication • Wasteful • Unnecessary copies of unused files • Not enough copies of heavily used files • Maintaining consistency causes performance problems • Caching + Replication • Combines Problems from both

  4. Solution – Public Caches • Use Whole File Caching as normal • Use AFS-like consistency semantics • Publish location of your copy in the file’s “inode” • Provides usage-based replication • Reduction in unnecessary copies • Semantics • Copy On Read • Clobber On Close

  5. Implementation – Multi-FS • Parrot • Type II VM • Transparent Remote Filesystem access • Home of Multi-FS • Chirp • Distributed Filesystem used by Multi-FS • Log-style Metadata • Cache Cleaner • Removes out-of-date versions • Reduces log to minimum necessary

  6. application open A@ex/foothen read into memory parrot open A/ex/root/foo open B/ex/data/abc return “B, /ex/data/abc” B(data only) A (metadata& data) return “Hello World 2” • B/ex/data/ • abc: “Hello World 2” • A/ex/root/ • foo: B, /ex/data/abc • bar: A, /ex/data/xyz • A/ex/data/ • xyz: “Hello World” Multi-FS

  7. Multi-FS w/Public Caches client application • client/multicache/ • mno: “Hello World 2” return “Hello World 2” open A@ex/foothen read into memory parrot open A/ex/root/foo open B/ex/data/abc return “B, /data/ex/abc” B(data only) A (metadata& data) • A/ex/root/ • foo: B, /data/ex/abc • client, /multicache/mno • bar: A, /data/ex/xyz • A/ex/data/ • xyz: “Hello World” • B/ex/data/ • abc: “Hello World 2”

  8. Evaluation • Overhead • Not substantially different • Clustered File Requests • Impact of File Write

  9. Conclusions • Public Caching Works • Public Caching provides performance benefits • Public Caching overhead is not excessive

  10. Questions?

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