Misplaced Pages

Sequential access

Article snapshot taken from[REDACTED] with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
(Redirected from Sequential I/O) Computer memory concept
This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these messages)
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.
Find sources: "Sequential access" – news · newspapers · books · scholar · JSTOR (June 2024) (Learn how and when to remove this message)
This article possibly contains original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (June 2024) (Learn how and when to remove this message)
(Learn how and when to remove this message)
Sequential access compared to random access

Sequential access is a term describing a group of elements (such as data in a memory array or a disk file or on magnetic-tape data storage) being accessed in a predetermined, ordered sequence. It is the opposite of random access, the ability to access an arbitrary element of a sequence as easily and efficiently as any other at any time.

Sequential access is sometimes the only way of accessing the data, for example if it is on a tape. It may also be the access method of choice, for example if all that is wanted is to process a sequence of data elements in order.

Definition

There is no consistent definition in computer science of sequential access or sequentiality. In fact, different sequentiality definitions can lead to different sequentiality quantification results. In spatial dimension, request size, stride distance, backward accesses, re-accesses can affect sequentiality. For temporal sequentiality, characteristics such as multi-stream and inter-arrival time threshold has impact on the definition of sequentiality.

In data structures, a data structure is said to have sequential access if one can only visit the values it contains in one particular order. The canonical example is the linked list. Indexing into a list that has sequential access requires O(n) time, where n is the index. As a result, many algorithms such as quicksort and binary search degenerate into bad algorithms that are even less efficient than their naive alternatives; these algorithms are impractical without random access. On the other hand, some algorithms, typically those that do not have index, require only sequential access, such as mergesort, and face no penalty.

See also

References

  1. Random and Sequential Data Access, Microsoft TechNet
  2. Irfan Ahmad, Easy and Efficient Disk I/O Workload Characterization in VMware ESX Server, IISWC, 2007.
  3. Eric Anderson, Capture, Conversion, and Analysis of an Intense NFS Workload, FAST, 2009.
  4. Yanpei Chen et al. Design Implications for Enterprise Storage Systems via Multi-dimensional Trace Analysis. SOSP. 2011
  5. Andrew Leung et al. Measurement and Analysis of Large-scale Network File System Workloads. USENIX ATC. 2008
  6. Frank Schmuck and Roger Haskin, GPFS: A Shared-Disk File System for Large Computing Clusters, FAST. 2002
  7. Alan Smith. Sequentiality and Prefetching in Database Systems. ACM TOS
  8. Hyong Shim et al. Characterization of Incremental Data Changes for Efficient Data Protection. USENIX ATC. 2013.
  9. Avishay Traeger et al. A Nine Year Study of File System and Storage Benchmarking. ACM TOS. 2007.
  10. Cheng Li et al. Assert(!Defined(Sequential I/O)). HotStorage. 2014
Category:
Sequential access Add topic