Cyclical Repetition of Data Schiller, Section 6.2 Emmanuel Agu CS - PowerPoint PPT Presentation

Cyclical Repetition of Data Schiller, Section 6.2 Emmanuel Agu CS Dept. WPI

Broacast Disks • Asymmetric communication environments – Assymetric bandwidth – Assymetric information access patterns • Data-specific optimizations – Client-server – Server pushing information – Broadcast disks abstraction • Broadcast disks – Possible only if knowledge of data content + access patterns 2 Worcester Polytechnic Institute

Unidirectional distribution service provider service user A B receiver A A B receiver A unidirectional A B sender distribution . medium . A . B A receiver optimized for expected ≠ individual access access pattern pattern of one user of all users 3 Worcester Polytechnic Institute

Structuring transmissions: broadcast disks • Sender – cyclic repetition of data blocks – different patterns possible flat disk A B C A B C skewed disk A A B C A A multi-disk A B A C A B • Receiver – use of caching • cost-based strategy: costs of user waiting if requested block is not cached • To optimize, application and cache have to know: 4 – data content + and user access patterns Worcester Polytechnic Institute

Broadcast disk example • Radio station transmitting – Block A: road conditions – Block B: weather report – Block C: latest events in town – Block D: Menu to access topics + music • May Generate: DADBDADCDADBDADC • Client program may add caching if user: – town events in evening => cache block C for evening – road conditions in morning => cache blk A in morning 5 Worcester Polytechnic Institute

Original paper • S. Acharya, R. Alonso, M. Franklin, and S. Zdonik, "Broadcast Disks: Data Management for Asymmetric Communication Environments," Proceedings of ACM SIGMOD'1995. • S. Acharya, "“Broadcast Disks”: Dissemination-based Data Management for Asymmetric Communication Environments," Ph.D. Thesis, Brown University, 1997. • Swarup Acharya – @ Lucent labs, NJ – More networking now 6 Worcester Polytechnic Institute