Mathematical Framework for A Novel Database Replication Algorithm

2011

In recent years, grid technology has had such a fast growth that it has been used in many scientific experiments and research centers. A large number of storage elements and computational resources are combined to generate a grid which gives us shared access to extra computing power. In particular, data grid deals with data intensive applications and provides intensive resources across widely distributed communities. Data replication is an efficient way for distributing replicas among the data grids, making it possible to access similar data in different locations of the data grid. Replication reduces data access time and improves the performance of the system. In this paper, we propose a new dynamic data replication algorithm named PDDRA that optimizes the traditional algorithms. Our proposed algorithm is based on an assumption: members in a VO (Virtual Organization) have similar interests in files. Based on this assumption and also file access history, PDDRA predicts future needs of grid sites and pre-fetches a sequence of files to the requester grid site, so the next time that this site needs a file, it will be locally available. This will considerably reduce access latency, response time and bandwidth consumption. PDDRA consists of three phases: storing file access patterns, requesting a file and performing replication and pre-fetching and replacement. The algorithm was tested using a grid simulator, OptorSim developed by European Data Grid projects. The simulation results show that our proposed algorithm has better performance in comparison with other algorithms in terms of job execution time, effective network usage, total number of replications, hit ratio and percentage of storage filled.

2011

The necessity of ever-increasing use of distributed data in computer networks is obvious for all. One technique that is performed on the distributed data for increasing of efficiency and reliablity is data rplication. In this paper, after introducing this technique and its advantages, we will examine some dynamic data replication. We will examine their characteristies for some overus scenario and the we will propose some suggestion for their improvement.

Database and Expert Systems …, 1996

In this paper we investigate the performance issues of data replication in a loosely coupled distributed database system, where a set of database servers are connected via a network. A database replication scheme, Replication with Divergence, which allows some degree of divergence between the primary and the secondary copies of the same data object, is compared to other two schemes that, respectively, disallows replication and maintains all replicated copies consistent at all times. The impact of some tunable factors, such as cache size and the update propagation probability, on the performance of Replication with Divergence is also investigated. These results shed light on the performance issues that were not addressed in previous studies on replication of distributed database systems.

International Journal of Computer and Communication Engineering, 2013

The production database are transactions intensive transactions can be insert, update on the tables, failover is the replica of the production server, if there is any change we have to implement on the production and it will be automatically implemented on failover or standby database. Now a days the data on the production server is increasing and we need extra storage space on production server to keep data and this is same required on the failover. To generate reports from that data will increase load on the production server and can affect the performance of the server. There are also some threats which can cause loss of data from which we have to protect our database like Hardware failure, loss of machine. Replication is one of the methods for Backup of the running database and its immediate failover during failure. This paper represents some parts for the replication techniques, failover, and transaction states.

International Journal of Intelligent Systems and Applications, 2015

Due to the emergence of more data centric applications, the replication of data has become a more common phenomenon. In the similar context, recently, (PDDRA) a Prefetching based dynamic data replication algorithm is developed. The main idea is to pre-fetch some data using the heuristic algorithm before actual replication start to reduce latency In the algorithm further modifications (M-PDDRA) are suggested to minimize the delay in data replication. In this paper, M-PDDRA algorithm is tested under shared and output buffering scheme. Simulation results are presented to estimate the packet loss rate and average delay for both shared and output buffered schemes. The simulation results clearly reveal that the shared buffering with load balancing scheme is as good as output buffered scheme with much less buffering resources.

International Journal on Information Theory, 2014

In this paper, a review for consistency of data replication protocols has been investigated. A brief deliberation about consistency models in data replication is shown. Also we debate on propagation techniques such as eager and lazy propagation. Differences of replication protocols from consistency view point are studied. Also the advantages and disadvantages of the replication protocols are shown. We advent into essential technical details and positive comparisons, in order to determine their respective contributions as well as restrictions are made. Finally, some literature research strategies in replication and consistency techniques are reviewed.

Data grids provide large-scale geographically distributed data resources for data intensive applications. These applications handle large data sets that need to be transferred and replicated among different grid sites so availability and efficient access are the most important factors affecting the performance. It is obvious that, managing the volume of data is very important. Data replication is an important technique to reduces data access time which improves the performance of the system by creating identical replicas of data files and distributing them on grid sites. In this paper, we propose a novel dynamic data replication strategy called DRPF (Dynamic Replication of Popular File), which is based on access history and file's popularity. As grid sites within a virtual organization(VO) have similar interest of files, the basic idea of DRPF is to improve locality in accesses through increasing the the number of replicas in the VO. DRPF first selects the popular files that are needed to be copied to other nodes, then tries to find the best places for placement of new replicas by taking into account parameters such as the number of demands per site for files and bandwidth between replication sites. The algorithm is simulated using a data grid simulator, OptorSim. The simulation results show that our proposed algorithm has better performance in comparison with other algorithms in terms of job execution time and effective network usage.

Replication is a well-known solution used to improve data availability. Data replication is one of the key components in data grid architecture, clustering and distributed system as it enhances data access and reliability and minimizes the cost of data transmission. This paper proposed a persistence layer synchronous replication technique (PSR). The persistence layer is a synchronous layer based on Computer threading technique .The whole system is a service oriented application. All the replication will have been done through the service oriented practices and in the new technique adding more replicated database server will be easier than ever.

Journal of Parallel and Distributed Computing, 2008

This paper compares and analyzes 10 heuristics to solve the fine-grained data replication problem over the Internet. In fine-grained replication, frequently accessed data objects (as opposed to the entire website contents) are replicated onto a set of selected sites so as to minimize the average access time perceived by the end users. The paper presents a unified cost model that captures the minimization of the total object transfer cost in the system, which in turn leads to effective utilization of storage space, replica consistency, fault-tolerance, and load-balancing. The set of heuristics include six A-Star based algorithms, two bin packing algorithms, one greedy and one genetic algorithm. The heuristics are extensively simulated and compared using an experimental test-bed that closely mimics the Internet infrastructure and user access patterns. GT-ITM and Inet topology generators are used to obtain 80 well-defined network topologies based on flat, link distance, power-law and hierarchical transit-stub models. The user access patterns are derived from real access logs collected at the websites of Soccer World Cup 1998 and NASA Kennedy Space Center. The heuristics are evaluated by analyzing the communication cost incurred due to object transfers under the variance of server capacity, object size, read access, write access, number of objects and sites. The main benefit of this study is to facilitate readers with the choice of algorithms that guarantee fast or optimal or both types of solutions. This allows the selection of a particular algorithm to be used in a given scenario.

2013

A Data Grid consists of a collection of geographically distributed computer and storage resources located in different places, and enables users to share data and other resources. Data replication is used in Data Grid to enhance data availability, fault tolerance, load balancing and reliability. Although replication is a key technique, but the problem of selecting proper locations for placing replicas i.e. replica placement in Data Grid has not been widely studied, yet. In this paper an efficient replica selection strategy is proposed to select the best replica location from among the many replicas. Due to the limited storage capacity, a good replica replacement algorithm is needed. We present a novel replacement strategy which deletes files in two steps when free space is not enough for the new replica. A Grid simulator, OptorSim, is used to evaluate the performance of this dynamic replication strategy. The simulation results show that the proposed algorithm outperforms comparing t...