Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

I/O Model of Computation

  • Donghui ZhangEmail author
  • Vassilis J. Tsotras
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_752


Disk-based model


The I/O model of computation measures the efficiency of an algorithm by counting how many disk reads and writes it needs. It is widely applicable to the database environment, since most data is stored on disks and disk access typically dominates CPU time.

Key Points

For many computing-intensive applications, the appropriate model of computation is to measure CPU time. Yet in data-intensive applications, such as databases, it is more relevant to measure the number of disk I/Os [1]. This is termed the “I/O model of computation,” or disk-based model. Nowadays, most hard drives use the seek-rotate-transfer protocol [2]. In order to transfer some data from disk to memory (so as the data can be processed by the CPU), or to transfer data back to disk, the hard drive needs first to spend some “seek time” to move the read/write head to the cylinder where the data is located at. Then the “rotational delay” is spent until the sector containing the data...

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Recommended Reading

  1. 1.
    Aggarwal A, Vitter JS. The input/output complexity of sorting and related problems. Commun ACM. 1988;31(9):1116–27.MathSciNetCrossRefGoogle Scholar
  2. 2.
    Ramakrishnan R, Gehrke J. Database management systems. 3rd ed. New York: McGraw-Hill; 2003.zbMATHGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Paradigm4, Inc.WalthamUSA
  2. 2.University of California-RiversideRiversideUSA

Section editors and affiliations

  • Vassilis J. Tsotras
    • 1
  1. 1.University of California-RiversideRiversideUSA