数据库资源高可用性的分析与设计

通过对当前数据库资源高可用性不足之处的分析,建立了主从式数据库系统的数据库资源高可用性模型,实现了异质数据库间高可用性的模块化,提出了基于日志传输的设计方案,保证了主从数据库数据的一致性与完整性。     

云平台中MySQL数据库高可用性的设计与实现

为解决OpenStack云平台中单个节点的MySQL数据库在面临高并发访问和海量数据增长的情况下存在可靠性低、存储扩展性差、单点瓶颈等问题,设计并实现一种以Ceph分布式文件系统为存储后端的高可用MySQL数据库集群系统。通过集群技术消除基于独立服务器的单点瓶颈问题,保障业务的可靠性和高可用性,设计一套优化模型提高故障切换效率,底层的Ceph分布式文件系统为数据存储提供扩展性和安全性。实验结果表明,该MySQL高可用集群可以实现存储的扩展和节点失效情况下的故障切换,该优化模型可以有效降低故障切换时间。     

Symmetric active/active metadata service for high availability parallel file systems

High availability data storage systems are critical for many applications as research and business become more data driven. Since metadata management is essential to system availability, multiple metadata services are used to improve the availability of distributed storage systems. Past research has focused on the active/standby model, where each active service has at least one redundant idle backup. However, interruption of service and even some loss of service state may occur during a fail-over depending on the replication technique used. In addition, the replication overhead for multiple metadata services can be very high. The research in this paper targets the symmetric active/active replication model, which uses multiple redundant service nodes running in virtual synchrony. In this model, service node failures do not cause a fail-over to a backup and there is no disruption of service or loss of service state. A fast delivery protocol is further discussed to reduce the latency of the total order broadcast needed. The prototype implementation shows that metadata service high availability can be achieved with an acceptable performance trade-off using the symmetric active/active metadata service solution.     

Piranha: a CORBA tool for high availability

Despite the most careful planning, system applications can be dogged by unexpected failures. Our firm is keenly aware of the need for availability. To help meet that need, I developed an experimental CORBA-based restart service and monitor called Piranha, which both monitors and manages distributed applications to help systems attain high availability. First, Piranha acts as a network monitor that reports failures through a graphical user interface. Second, Piranha acts as a manager: it automatically restarts failed CORBA objects, replicates stateful objects (objects that maintain an internal set of values) on-the-fly, migrates objects from one host to another and enforces predefined replication degrees-numbers of copies-on groups of objects. As a backdrop to the discussion of Piranha's design and implementation, this article first examines the ways in which a CORBA ORB should support availability. I then explain how Piranha affords availability     

Expert systems for database design: A comparative review

Various researchers have applied artificial intelligence technology in the form of export systems to the process of database design. This report examines several approaches, comparing them using the following criteria: stage of database design supported, type of user interface employed, method used to drive the design process, whether the approach possesses any domain specific knowledge, database design technique used, whether the undoing of design states is permitted, and whether any learning capability is present. Several approaches are examined, either due to their historical significance, or because they illustrate a specific point of interest relating to the problem. Two distinct groups of systems are identified, those accommodating direct contact by users, and those relying on externally provided information. The report concludes by discussing the current state of the subject area, and recommends that an area for future development be the application of the technique to the design of structures capable of increased semantic content.     

FAST: Flash-aware external sorting for mobile database systems

Recently, flash memory has gained its popularity as storage on wide spectrum of computing devices such as cellular phones, digital cameras, digital audio players and PDAs. The integration of high-density flash memory has been accelerated twice every year for past few years. As flash memory’s capacity increases and its price drops, it is expected that flash memory will be more competitive with magnetic disk drives. Therefore, it is desirable to adapt disk-based algorithms to take advantage of the flash memory technology.In this paper, we propose a novel Flash-Aware external SorTing algorithm, FAST, that overcomes the limitation of larger writing cost for flash memory to improve both overall execution time and response time. In FAST, we reduce the write operations with additional read operations. We provide the analysis for both traditional and our flash-aware algorithms by comparing the detailed cost formulas. Experimental results with synthetic and real-life data sets show that FAST can result in faster execution time as well as smaller response time than traditional external sorting algorithms.     

Index organizations for object-oriented database systems

We present an indexing technique providing support for queries involving complex, nested objects and inheritance hierarchies. This technique is compared with two techniques obtained from more traditional organizations. The three techniques are evaluated using an analytical cost model. The discussion is cast in the framework of object-oriented databases. However, results are applicable to data management systems characterized by features such as complex objects and inheritance hierarchies     

General purpose schedulers for database systems

Summary A family of simple models for database systems is defined, where a system is composed of a scheduler, a data manager and several user transactions. The basic correctness criterion for such systems is taken to be consistency preservation. The central notion of the paper is that of a general purpose scheduler, a database system scheduler that is blind to the semantics of transactions and integrity assertions. Consistency preservation of a database system is shown to be precisely equivalent to a restriction on the output of a general purpose scheduler GPS, called weak serializability. That is, any database system using GPS will preserve consistency iff the output of GPS is always weakly serializable. This establishes a tight connection between database system correctness and scheduler behavior. Also, aspects of restart facilities and predeclared data accesses are discussed. Finally, several examples of schedulers correct with respect to weak serializability are presented.     

Optimal semijoins for distributed database systems

A Bloom-filter-based semijoin algorithm for distributed database systems is presented. This algorithm reduces communications costs to process a distributed natural join as much as possible with a filter approach. An optimal filter is developed in pieces. Filter information is used both to recognize when the semijoin will cease to be effective and to optimally process the semijoin. An ineffective semijoin will be quickly and cheaply recognized. An effective semijoin will use all of the transmitted bits optimally     

Image database systems: A survey

In this paper the state of image database (IDB) systems which have been developed in the past few years is reviewed. We point out the essential problems in IDB design rather than classify the existing or proposed systems into an unestablished framework. After giving a general overview, the approaches to IDB and the elements of IDB systems are discussed. Finally, several representative IDB systems are presented.     

Divergence control for distributed database systems

This paper presents distributed divergence control algorithms for epsilon serializability for both homogeneous and heterogeneous distributed databases. Epsilon serializability allows for more concurrency by permitting non-serializable interleavings of database operations among epsilon transactions. We first present a strict 2-phase locking divergence control algorithm and an optimistic divergence control algorithm for a homogeneous distributed database system, where the local orderings of all the sub-transactions of a distributed epsilon transaction are the same. In such an environment, the total inconsistency of a distributed epsilon transaction is simply the sum of those of all its sub-transactions. We then describe a divergence control algorithm for a heterogeneous distributed database system, where the local orderings of all the sub-transactions of a distributed epsilon transaction may not be the same and the total inconsistency of a distributed epsilon transaction may be greater than the sum of those of all its sub-transactions. As a result, in addition to executing a local divergence control algorithm in each site to maintain the local inconsistency, a global mechanism is needed to take into account the additional inconsistency Recommended by: Meichum Hsu     

VLSI accelerators for large database systems

An experimental VLSI accelerator research prototype designed and fabricated for relational data filtering is described. It performs high-speed associative search and aggregation operations for formatted databases. For unformatted databases, an experimental fast string search VLSI accelerator that provides a few orders-of-magnitude improvement in text search speed has been developed. The VLSI accelerators have precise instruction sets and hardware interfaces that facilitate their integration into general-purpose computer systems and dedicated systems. Application of the accelerators to both general-purpose and dedicated computer systems is discussed. Related work is examined     

Coupling production systems and database systems: a homogeneousapproach

Methods for storing and manipulating large rule bases using a relational database management systems (DBMS) are discussed. An approach to decomposing and storing the condition elements in the antecedents of rules such as those used in production rule-based systems is presented. A set-oriented approach, DBCond, which uses a special data structure that is implemented using relations is proposed. A matching algorithm for DBCond uses the relational structures to efficiently identify rules whose antecedents are satisfied. The performance of DBCond is compared with that of DBRete, a DBMS implementation of the Rete match algorithm developed for use with the production rule language OPS5. DBCond is also compared with DBQuery, a method that is based on evaluating queries corresponding to the conditions in the antecedents of the rules. Improvements to the data structure and the algorithms of the DBCond method are described. An advantage of DBCond is that it is fully parallelizable, thus making it attractive for parallel computing environments     

Cooperative database systems

In recent years, there has been considerable interest in techniques that enhance the cooperative behavior of database systems and many different techniques have been developed. These techniques approach the goal of cooperation in diverse ways; the differences may be in the specific task in which they offer cooperation, in the details of the solution, and even in the very interpretation of cooperative behavior. In this article we classify many different techniques into categories of cooperation, and we survey the techniques in some of these categories. Finally, we consider the challenges that remain and offer directions for new research. © 1996 John Wiley & Sons, Inc.     

Wcrl: A data model independent language for database systems

The need for data model independent languages for database systems has become apparent in recent years. They can be used for the conceptual level of a database system, for communication in a distributed database system, for data restructuring, and so on. This paper proposes a language,wcrl, to fill this need and compares it with the very few other languages which have been developed almost concurrently to fill the same need.     

PressBase : a presentation synchronization database for distributed multimedia systems

Multimedia presentations are the basic objects of multimedia databases. Since a multimedia presentation is not an instant display of a query result, the control knowledge (or synchronization requirements) has to be incorporated into the database and necessary precautions have to be taken for a lengthy presentation. Active databases provide a mechanism for incorporation of control knowledge by using event-condition-action (ECA) rules. In this paper, we describe how multimedia synchronization can be handled within a database using ECA rules. We present a prototype presentation synchronization database, named as PressBase, for distributed multimedia systems. We have adopted one of the synchronization models, SynchRuler, and then incorporated into a relational database system.