In this paper we present recovery techniques for distributed main-memory databases, specifically for client-server and shared-disk architectures. We present a recovery scheme for client-server architectures which is b...
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ISBN:
(纸本)081867475X
In this paper we present recovery techniques for distributed main-memory databases, specifically for client-server and shared-disk architectures. We present a recovery scheme for client-server architectures which is based on shipping log records to the server, and two recovery schemes for shared-disk architectures-one based on page shipping, and the other based on broadcasting of the log of updates. The schemes offer different tradeoffs, based on factors such as update rates. Our techniques are extensions to a distributed-memory setting of a centralized recovery scheme for main-memory databases, which has been implemented in the Dali main-memory database system. Our centralized as well as distributed-memory recovery schemes have several attractive features-they support an explicit multi-level recovery abstraction for high concurrency, reduce disk I/O by writing only redo log records to disk during normal processing, and use per-transaction redo and undo logs to reduce contention on the system log. Further, the techniques use a fuzzy checkpointing scheme that writes only dirty pages to disk, yet minimally interferes with normal processing-all but one of our recovery schemes do not require updaters to even acquire a latch before updating a page. Our log shipping/broadcasting schemes also support concurrent updates to the same page at different sites.
distributed storage systems introduce redundancy to protect data from node failures. After a storage node fails, the lost data should be regenerated at a replacement storage node as soon as possible to maintain the sa...
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ISBN:
(纸本)9781467375887
distributed storage systems introduce redundancy to protect data from node failures. After a storage node fails, the lost data should be regenerated at a replacement storage node as soon as possible to maintain the same level of redundancy. Minimizing such a regeneration time is critical to the reliability of distributed storage systems. Existing work commits to reduce the regeneration time by either minimizing the regenerating traffic, or adjusting the regenerating traffic patterns, whereas nodes participating the regeneration are generally assumed to be given beforehand. However, real-world distributed storage systems usually exhibit heterogeneous link capacities, and the regeneration time is highly related to the selection of the participating nodes. In this paper, we consider the minimization of the regeneration time by selecting the participating nodes in heterogeneous networks. We propose optimal node selection algorithms respectively for two cases: 1) the newcomer is not given;2) both the newcomer and the providers are not given. Analysis shows that the optimal regeneration time can be achieved in each case. We then consider the effect of flexible amount of data blocks from each provider on the regeneration time, and apply this observation to enhance our schemes. Experiment results show that our node selection schemes can significantly reduce the regeneration time, especially in practical networks with heterogeneous link capacities, compared with the scheme based on random node selection.
BLAST (Basic Local Alignment Search Tool) is by far the most widely used application for rapid screening of large sequence databases. This paper describes TurboBLAST, a parallel implementation of BLAST suitable for ex...
Current processor allocation techniques for highly parallelsystems are based on centralized front-end based algorithms. As a result, the applied strategies are restricted to static allocation, low parallelism and wea...
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ISBN:
(纸本)0769507840
Current processor allocation techniques for highly parallelsystems are based on centralized front-end based algorithms. As a result, the applied strategies are restricted to static allocation, low parallelism and weak fault tolerance. To lift these restrictions we are investigating a distributed approach to the processor allocation problem in large distributed memory machines. A contiguous and a noncontiguous version of a distributed dynamic processor allocation strategy are proposed and studied in this paper Simulations compare the performance of the proposed strategies with that of well-known centralized algorithms. We also present the results of experiments on a Simens hpcLine Primergy Sewer with 96 nodes that show distributed allocation is feasible with current technologies.
TOP-C is a task-oriented parallel C interface. It presents a master-slave task architecture that greatly eases the parallelization of code. It is intended for applications where a compiler would have difficulty recogn...
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ISBN:
(纸本)0818675829
TOP-C is a task-oriented parallel C interface. It presents a master-slave task architecture that greatly eases the parallelization of code. It is intended for applications where a compiler would have difficulty recognizing opportunities for data-parallelism. The model has been implemented for both shared memory processors and networks of workstations. There is also a sequential version useful during development, which runs the same application code. Ease-of-use has been a strong motivation behind its design. For this reason, TOP-C is organized in a SPMD style, with one primary subroutine call to invoke it. Its main features are: (a) task-parallelism, (b) a single shared, global data structure, and (c) restricted master-slave communication.
A new parallel algorithm, based on the concept of antidiagonal wave pattern, for computing approximate inverses, is introduced for symmetric multiprocessor systems. The parallel normalized approximate inverses are use...
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ISBN:
(纸本)9780769534725
A new parallel algorithm, based on the concept of antidiagonal wave pattern, for computing approximate inverses, is introduced for symmetric multiprocessor systems. The parallel normalized approximate inverses are used in conjunction with parallel normalized preconditioned conjugate gradient-type schemes, for the efficient solution of sparse finite element linear systems. The parallel implementation issues of the new algorithm are discussed and the parallel performance is presented, using OpenMP.
Exploratory Visualization is an approach for helping users learn about distributed computations without requiring users to examine source code. Instead visualizations provide intuition about the program's behavior...
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ISBN:
(纸本)0769506348
Exploratory Visualization is an approach for helping users learn about distributed computations without requiring users to examine source code. Instead visualizations provide intuition about the program's behavior and serve as an interface through which the programs are controlled. We have developed an exploratory visualization system with the goals of providing an intuitive and user-friendly user interface and developing an infrastructure that minimizes perturbation. We present a case-study to describe how a naive user can interact with the system to learn about and experiment with the running computation.
The paper deals with the distributed learning. distributed learning from data is considered to be an important challenge faced by researchers and practice in the domain of the distributed data mining and distributed k...
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ISBN:
(纸本)9781457706530
The paper deals with the distributed learning. distributed learning from data is considered to be an important challenge faced by researchers and practice in the domain of the distributed data mining and distributed knowledge discovery from databases. An effective approach to learning from a geographically distributed data is to select, from the local databases, relevant local patterns, called also prototypes. Such a selection can be based on results of the data reduction process. The paper proposes to carry-out prototype selection at local sites in parallel, independently at each site, employing specialized software agents. To assure obtaining homogenous prototypes at a global level the consensus-based method is proposed and applied. The paper includes a detailed description of the proposed approach and a discussion of the computational experiment results.
The establishment of one logical database that spans countries and continents is increasingly becoming a realistic goal to achieve. This conceptual database would potentially consist of an ever growing number of compo...
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The establishment of one logical database that spans countries and continents is increasingly becoming a realistic goal to achieve. This conceptual database would potentially consist of an ever growing number of component databases. In this paper, we propose a scheme to build a Worldwide Database using a two-level approach. In particular, we describe how conglomerations (small and large) of databases are formed, modified, and evolved.
distributed OLTP systems execute the high-overhead, two-phase commit (2PC) protocol at the end of every distributed transaction. Epoch-based commit proposes that 2PC be executed only once for all transactions processe...
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ISBN:
(纸本)9781665497534
distributed OLTP systems execute the high-overhead, two-phase commit (2PC) protocol at the end of every distributed transaction. Epoch-based commit proposes that 2PC be executed only once for all transactions processed within a time interval called an epoch. Increasing epoch duration allows more transactions to be processed before the common 2PC. It thus reduces 2PC overhead per transaction, increases throughput but also increases average transaction latency. Therefore, required is the ability to choose the right epoch size that offers the desired trade-off between throughput and latency. To this end, we develop two analytical models to estimate throughput and average latency in terms of epoch size taking into account load and failure conditions. Simulations affirm their accuracy and effectiveness. We then present epoch-based multi-commit which, unlike epoch-based commit, seeks to avoid all transactions being aborted when failures occur, and also performs identically when failures do not occur. Our performance study identifies workload factors that make it more effective in preventing transaction aborts and concludes that the analytical models can be equally useful in predicting its performance as well.
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