Lecture_21 - Chapter 6 Storage and Other I/O Topics I/O...

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Chapter 6 Storage and Other I/O Topics
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Chapter 6 — Storage and Other I/O Topics — 2 Measuring I/O Performance I/O performance depends on Hardware: CPU, memory, controllers, buses Software: operating system, database management system, application Workload: request rates and patterns I/O system design can trade-off between response time and throughput Measurements of throughput often done with constrained response-time §6.7 I/O Performance Measures: …
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Chapter 6 — Storage and Other I/O Topics — 3 Transaction Processing Benchmarks Transactions Small data accesses to a DBMS Interested in I/O rate, not data rate Measure throughput Subject to response time limits and failure handling ACID (Atomicity, Consistency, Isolation, Durability) Overall cost per transaction Transaction Processing Council (TPC) benchmarks ( www.tpc.org ) TPC-APP: B2B application server and web services TPC-C: on-line order entry environment TPC-E: on-line transaction processing for brokerage firm TPC-H: decision support — business oriented ad-hoc queries
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Chapter 6 — Storage and Other I/O Topics — 4 File System & Web Benchmarks SPEC System File System (SFS) Synthetic workload for NFS server, based on monitoring real systems Results Throughput (operations/sec) Response time (average ms/operation) SPEC Web Server benchmark Measures simultaneous user sessions, subject to required throughput/session Three workloads: Banking, Ecommerce, and Support
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Chapter 6 — Storage and Other I/O Topics — 5 I/O vs. CPU Performance Amdahl’s Law Don’t neglect I/O performance as parallelism increases compute performance Example Benchmark takes 90s CPU time, 10s I/O time Double the number of CPUs/2 years I/O unchanged Year CPU time I/O time Elapsed time % I/O time now 90s 10s 100s 10% +2 45s 10s 55s 18% +4 23s 10s 33s 31% +6 11s 10s 21s 47% §6.9 Parallelism and I/O: RAID
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Chapter 6 — Storage and Other I/O Topics — 6 RAID Redundant Array of Inexpensive (Independent) Disks Use multiple smaller disks (c.f. one large disk) Parallelism improves performance Plus extra disk(s) for redundant data storage Provides fault tolerant storage system Especially if failed disks can be “hot swapped” RAID 0 No redundancy (“AID”?) Just stripe data over multiple disks But it does improve performance
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This note was uploaded on 03/07/2012 for the course CS 2506 taught by Professor Srinidhivaradarajan during the Spring '12 term at Virginia Tech.

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Lecture_21 - Chapter 6 Storage and Other I/O Topics I/O...

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