Department of Computer Science and Technology

Technical reports

HARP: a hierarchical asynchronous replication protocol for massively replicated systems

Noha Adly

August 1993, 34 pages

DOI: 10.48456/tr-310


This paper presents a new asynchronous replication protocol that is especially suitable for wide area and mobile systems, and allows reads and writes to occur at any replica. Updates reach other replicas using a propagation scheme based on nodes organized into a logical hierarchy. The hierarchical structure enables the scheme to scale well for thousands of replicas, while ensuring reliable delivery. A new service interface is proposed that provides different levels of asynchrony, allowing strong consistency and weak consistency to be integrated into the same framework. Further, due to the hierarchical pattern of propagation, the scheme provides the ability to locate replicas that are more up-to-date than others, depending on the needs of various applications. Also, it allows a selection from a number of reconciliation techniques based on delivery order mechanisms. Restructuring operations are provided to build and reconfigure the hierarchy dynamically without disturbing normal operations. The scheme tolerates transmission failures and network partitions.

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BibTeX record

  author =	 {Adly, Noha},
  title = 	 {{HARP: a hierarchical asynchronous replication protocol for
         	   massively replicated systems}},
  year = 	 1993,
  month = 	 aug,
  url = 	 {},
  institution =  {University of Cambridge, Computer Laboratory},
  doi = 	 {10.48456/tr-310},
  number = 	 {UCAM-CL-TR-310}