Lazy Database Replication with Ordering Guarantees
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Quantum Dxi4500 User's Guide
User’s Guide User’s Guide User’s Guide User’s Guide QuantumQuantum DXDXii45004500 DX i -Series 6-66904-01 Rev C DXi4500 User’s Guide, 6-66904-01 Rev C, August 2010, Product of USA. Quantum Corporation provides this publication “as is” without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability or fitness for a particular purpose. Quantum Corporation may revise this publication from time to time without notice. COPYRIGHT STATEMENT © 2010 Quantum Corporation. All rights reserved. Your right to copy this manual is limited by copyright law. Making copies or adaptations without prior written authorization of Quantum Corporation is prohibited by law and constitutes a punishable violation of the law. TRADEMARK STATEMENT Quantum, the Quantum logo, DLT, DLTtape, the DLTtape logo, Scalar, and StorNext are registered trademarks of Quantum Corporation, registered in the U.S. and other countries. Backup. Recovery. Archive. It’s What We Do., the DLT logo, DLTSage, DXi, DXi-Series, Dynamic Powerdown, FastSense, FlexLink, GoVault, MediaShield, Optyon, Pocket-sized. Well-armored, SDLT, SiteCare, SmartVerify, StorageCare, Super DLTtape, SuperLoader, and Vision are trademarks of Quantum. LTO and Ultrium are trademarks of HP, IBM, and Quantum in the U.S. and other countries. All other trademarks are the property of their respective companies. Specifications are subject to change without notice. ii Quantum DXi4500 User’s Guide Contents Preface xv Chapter 1 DXi4500 System Description 1 Overview . 1 Features and Benefits . 3 Data Reduction . 3 Data Deduplication . 3 Compression. 4 Space Reclamation . 4 Remote Replication . 5 DXi4500 System . -
Replication Using Group Communication Over a Partitioned Network
Replication Using Group Communication Over a Partitioned Network Thesis submitted for the degree “Doctor of Philosophy” Yair Amir Submitted to the Senate of the Hebrew University of Jerusalem (1995). This work was carried out under the supervision of Professor Danny Dolev ii Acknowledgments I am deeply grateful to Danny Dolev, my advisor and mentor. I thank Danny for believing in my research, for spending so many hours on it, and for giving it the theoretical touch. His warm support and patient guidance helped me through. I hope I managed to adopt some of his professional attitude and integrity. I thank Daila Malki for her help during the early stages of the Transis project. Thanks to Idit Keidar for helping me sharpen some of the issues of the replication server. I enjoyed my collaboration with Ofir Amir on developing the coloring model of the replication server. Many thanks to Roman Vitenberg for his valuable insights regarding the extended virtual synchrony model and the replication algorithm. I benefited a lot from many discussions with Ahmad Khalaila regarding distributed systems and other issues. My thanks go to David Breitgand, Gregory Chokler, Yair Gofen, Nabil Huleihel and Rimon Orni, for their contribution to the Transis project and to my research. I am grateful to Michael Melliar-Smith and Louise Moser from the Department of Electrical and Computer Engineering, University of California, Santa Barbara. During two summers, several mutual visits and extensive electronic correspondence, Louise and Michael were involved in almost every aspect of my research, and unofficially served as my co-advisors. The work with Deb Agarwal and Paul Ciarfella on the Totem protocol contributed a lot to my understanding of high-speed group communication. -
An Efficient Concurrency Control Technique for Mobile Database Environment by Md
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Global Journal of Computer Science and Technology (GJCST) Global Journal of Computer Science and Technology Software & Data Engineering Volume 13 Issue 2 Version 1.0 Year 2013 Type: Double Blind Peer Reviewed International Research Journal Publisher: Global Journals Inc. (USA) Online ISSN: 0975-4172 & Print ISSN: 0975-4350 An Efficient Concurrency Control Technique for Mobile Database Environment By Md. Anisur Rahman Dhaka University of Engineering & Technology Gazipur, Bangladesh Abstract - Day by day, wireless networking technology and mobile computing devices are becoming more popular for their mobility as well as great functionality. Now it is an extremely growing demand to process mobile transactions in mobile databases that allow mobile users to access and operate data anytime and anywhere, irrespective of their physical positions. Information is shared among multiple clients and can be modified by each client independently. However, for the assurance of timely access and correct results in concurrent mobile transactions, concurrency control techniques (CCT) happen to be very difficult. Due to the properties of Mobile databases e.g. inadequate bandwidth, small processing capability, unreliable communication, mobility etc. existing mobile database CCTs cannot employ effectively. With the client-server model, applying common classic pessimistic techniques of concurrency control (like 2PL) in mobile database leads to long duration Blocking and increasing waiting time of transactions. Because of high rate of aborting transactions, optimistic techniques aren`t appropriate in mobile database as well. This paper discusses the issues that need to be addressed when designing a CCT technique for Mobile databases, analyses the existing scheme of CCT and justify their performance limitations. -
A View-Based Approach to Relaxing Global Serializability in Multidatabase Systems
Purdue University Purdue e-Pubs Department of Computer Science Technical Reports Department of Computer Science 1993 A View-Based Approach to Relaxing Global Serializability in Multidatabase Systems Aidong Zhang Evaggelia Pitoura Bharat K. Bhargava Purdue University, [email protected] Report Number: 93-082 Zhang, Aidong; Pitoura, Evaggelia; and Bhargava, Bharat K., "A View-Based Approach to Relaxing Global Serializability in Multidatabase Systems" (1993). Department of Computer Science Technical Reports. Paper 1095. https://docs.lib.purdue.edu/cstech/1095 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. A VIEW-BASED APPROACH TO RELAXING GLOBAL SERIALIZABILITY IN MULTIDATABASE SYSTEMS Aldong Zhang Evaggelia PitOUI'3 Bharat Bh:Jrgava CSD TR-9J.082 December 1993 (Revised March 1994) A View-Based Approach to Relaxing Global Serializability in Multidatabase Systems Aidong Zhang, Evaggelia Pitoura, and Bharat K Bhargava Department of Computer Science Purdue University West Lafayette, IN 47907 USA Abstract In this paper, we propose a new approach to ensuring the correctness of non serializable executions. The approach is based on relating transaction views of the database to the integrity constraints of the system. Drawing upon this approach, we de velop a new correctness criterion for multidatabase concurrency control. This criterion, caUed view-based two-level serializability, relaxes global serializabitity in multidatabase systems while respecting the autonomy of local database systems. No additional re strictions other than serializallility are imposed on local database systems. 1 Introduction A Illultidataba.-<;e system (MDBS) is a higher-level confederation of a nWllber of pre-existing autonomolls and possibly heterogeneous database systems. -
Replication Vs. Caching Strategies for Distributed Metadata Management in Cloud Storage Systems
ShardFS vs. IndexFS: Replication vs. Caching Strategies for Distributed Metadata Management in Cloud Storage Systems Lin Xiao, Kai Ren, Qing Zheng, Garth A. Gibson Carnegie Mellon University {lxiao, kair, zhengq, garth}@cs.cmu.edu Abstract 1. Introduction The rapid growth of cloud storage systems calls for fast and Modern distributed storage systems commonly use an archi- scalable namespace processing. While few commercial file tecture that decouples metadata access from file read and systems offer anything better than federating individually write operations [21, 25, 46]. In such a file system, clients non-scalable namespace servers, a recent academic file sys- acquire permission and file location information from meta- tem, IndexFS, demonstrates scalable namespace processing data servers before accessing file contents, so slower meta- based on client caching of directory entries and permissions data service can degrade performance for the data path. Pop- (directory lookup state) with no per-client state in servers. In ular new distributed file systems such as HDFS [25] and the this paper we explore explicit replication of directory lookup first generation of the Google file system [21] have used cen- state in all servers as an alternative to caching this infor- tralized single-node metadata services and focused on scal- mation in all clients. Both eliminate most repeated RPCs to ing only the data path. However, the single-node metadata different servers in order to resolve hierarchical permission server design limits the scalability of the file system in terms tests. Our realization for server replicated directory lookup of the number of objects stored and concurrent accesses to state, ShardFS, employs a novel file system specific hybrid the file system [40]. -
Concurrency Control Basics
Outline l Introduction/problems, l definitions Introduction/ (transaction, history, conflict, equivalence, Problems serializability, ...), Definitions l locking. Chapter 2: Locking Concurrency Control Basics Klemens Böhm Distributed Data Management: Concurrency Control Basics – 1 Klemens Böhm Distributed Data Management: Concurrency Control Basics – 2 Atomicity, Isolation Synchronisation, Distributed (1) l Transactional guarantees – l Essential feature of databases: in particular, atomicity and isolation. Many users can access the same data concurrently – be it read, be it write. Introduction/ l Atomicity Introduction/ Problems Problems u Example, „bank scenario“: l Consistency must be guaranteed – Definitions Definitions task of synchronization component. Locking Number Person Balance Locking Klemens 5000 l Multi-user mode shall be hidden from users as far as possible: concurrent processing Gunter 200 of requests shall be transparent, u Money transfer – two elementary operations. ‚illusion‘ of being the only user. – debit(Klemens, 500), – credit(Gunter, 500). l Isolation – can be explained with this example, too. l Transactions. Klemens Böhm Distributed Data Management: Concurrency Control Basics – 3 Klemens Böhm Distributed Data Management: Concurrency Control Basics – 4 Synchronisation, Distributed (2) Synchronization in General l Serial execution of application programs Uncontrolled non-serial execution u achieves that illusion leads to other problems, notably inconsistency: l Introduction/ without any synchronization effort, Introduction/ -
Replication As a Prelude to Erasure Coding in Data-Intensive Scalable Computing
DiskReduce: Replication as a Prelude to Erasure Coding in Data-Intensive Scalable Computing Bin Fan Wittawat Tantisiriroj Lin Xiao Garth Gibson fbinfan , wtantisi , lxiao , garth.gibsong @ cs.cmu.edu CMU-PDL-11-112 October 2011 Parallel Data Laboratory Carnegie Mellon University Pittsburgh, PA 15213-3890 Acknowledgements: We would like to thank several people who made significant contributions. Robert Chansler, Raj Merchia and Hong Tang from Yahoo! provide various help. Dhruba Borthakur from Facebook provides statistics and feedback. Bin Fu and Brendan Meeder gave us their scientific applications and data-sets for experimental evaluation. The work in this paper is based on research supported in part by the Betty and Gordon Moore Foundation, by the Department of Energy, under award number DE-FC02-06ER25767, by the Los Alamos National Laboratory, by the Qatar National Research Fund, under award number NPRP 09-1116-1-172, under contract number 54515- 001-07, by the National Science Foundation under awards CCF-1019104, CCF-0964474, OCI-0852543, CNS-0546551 and SCI-0430781, and by Google and Yahoo! research awards. We also thank the members and companies of the PDL Consortium (including APC, EMC, Facebook, Google, Hewlett-Packard, Hitachi, IBM, Intel, Microsoft, NEC, NetApp, Oracle, Panasas, Riverbed, Samsung, Seagate, STEC, Symantec, and VMware) for their interest, insights, feedback, and support. Keywords: Distributed File System, RAID, Cloud Computing, DISC Abstract The first generation of Data-Intensive Scalable Computing file systems such as Google File System and Hadoop Distributed File System employed n (n ≥ 3) replications for high data reliability, therefore delivering users only about 1=n of the total storage capacity of the raw disks. -
Effective Technique for Optimizing Timestamp Ordering in Read- Write/Write-Write Operations
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 09 | Sep 2019 www.irjet.net p-ISSN: 2395-0072 Effective Technique for Optimizing Timestamp Ordering in Read- Write/Write-Write Operations Obi, Uchenna M1, Nwokorie, Euphemia C2, Enwerem, Udochukwu C3, Iwuchukwu, Vitalis C4 1Lecturer, Department of Computer Science, Federal University of Technology, Owerri, Nigeria 2Senior Lecturer, Department of Computer Science, Federal University of Technology, Owerri, Nigeria 3Lecturer, Department of Computer Science, Federal University of Technology, Owerri, Nigeria 4Lecturer, Department of Computer Science, Federal University of Technology, Owerri, Nigeria ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract - In recent times, the use of big data has been the measures, these are: read-write (RW) synchronization and trending technology, most enterprises tend to adopt large write-write (WW) synchronization. databases, but the inherent problem is how to ensure serializability in concurrent transactions that may want to Concurrency control techniques are employed for managing access the data in the database so as to maintain its data concurrent access of transactions on a particular data item integrity and not to compromise it. The aim of this research is by ensuring serializable executions or to avoid interference to develop an efficient Timestamp Ordering algorithm and among transactions and thereby helps in avoiding errors and model in conflicting operations in read-write/write-write data maintain consistency of the database. Various concurrency synchronization. In read-write synchronization, one of the control techniques have been developed by different operations to perform is read while the other is write researchers and these techniques are distinct and unique in operation. -
Middleware-Based Database Replication: the Gaps Between Theory and Practice
Appears in Proceedings of the ACM SIGMOD Conference, Vancouver, Canada (June 2008) Middleware-based Database Replication: The Gaps Between Theory and Practice Emmanuel Cecchet George Candea Anastasia Ailamaki EPFL EPFL & Aster Data Systems EPFL & Carnegie Mellon University Lausanne, Switzerland Lausanne, Switzerland Lausanne, Switzerland [email protected] [email protected] [email protected] ABSTRACT There exist replication “solutions” for every major DBMS, from Oracle RAC™, Streams™ and DataGuard™ to Slony-I for The need for high availability and performance in data Postgres, MySQL replication and cluster, and everything in- management systems has been fueling a long running interest in between. The naïve observer may conclude that such variety of database replication from both academia and industry. However, replication systems indicates a solved problem; the reality, academic groups often attack replication problems in isolation, however, is the exact opposite. Replication still falls short of overlooking the need for completeness in their solutions, while customer expectations, which explains the continued interest in developing new approaches, resulting in a dazzling variety of commercial teams take a holistic approach that often misses offerings. opportunities for fundamental innovation. This has created over time a gap between academic research and industrial practice. Even the “simple” cases are challenging at large scale. We deployed a replication system for a large travel ticket brokering This paper aims to characterize the gap along three axes: system at a Fortune-500 company faced with a workload where performance, availability, and administration. We build on our 95% of transactions were read-only. Still, the 5% write workload own experience developing and deploying replication systems in resulted in thousands of update requests per second, which commercial and academic settings, as well as on a large body of implied that a system using 2-phase-commit, or any other form of prior related work. -
Cache Serializability: Reducing Inconsistency in Edge Transactions
Cache Serializability: Reducing Inconsistency in Edge Transactions Ittay Eyal Ken Birman Robbert van Renesse Cornell University tributed databases. Until recently, technical chal- Abstract—Read-only caches are widely used in cloud lenges have forced such large-system operators infrastructures to reduce access latency and load on to forgo transactional consistency, providing per- backend databases. Operators view coherent caches as object consistency instead, often with some form of impractical at genuinely large scale and many client- facing caches are updated in an asynchronous manner eventual consistency. In contrast, backend systems with best-effort pipelines. Existing solutions that support often support transactions with guarantees such as cache consistency are inapplicable to this scenario since snapshot isolation and even full transactional atom- they require a round trip to the database on every cache icity [9], [4], [11], [10]. transaction. Our work begins with the observation that it can Existing incoherent cache technologies are oblivious to be difficult for client-tier applications to leverage transactional data access, even if the backend database supports transactions. We propose T-Cache, a novel the transactions that the databases provide: trans- caching policy for read-only transactions in which incon- actional reads satisfied primarily from edge caches sistency is tolerable (won’t cause safety violations) but cannot guarantee coherency. Yet, by running from undesirable (has a cost). T-Cache improves cache consis- cache, client-tier transactions shield the backend tency despite asynchronous and unreliable communication database from excessive load, and because caches between the cache and the database. We define cache- are typically placed close to the clients, response serializability, a variant of serializability that is suitable latency can be improved. -
On Ordering Transaction Commit
On Ordering Transaction Commit Mohamed M. Saad Roberto Palmieri Binoy Ravindran Virginia Tech msaad, robertop, binoy @vt.edu { } Complete Commit Execute Abstract Ordering In this poster paper, we briefly introduce an effective solution to Time address the problem of committing transactions enforcing a pre- α defined order. To do that, we overview the design of two algorithms γ that deploy a cooperative transaction execution that circumvents the δ transaction isolation constraint in favor of propagating written val- β ues among conflicting transactions. A preliminary implementation shows that even in the presence of data conflicts, the proposed al- gorithms outperform other competitors, significantly. Categories and Subject Descriptors D.1.3 [Software]: Concur- rent Programming; H.2.4 [Systems]: Transaction processing (a) BS 4 Thr. (b) BS 8 Thr. (c) FH Commit (d) FH Complete Keywords Transactional Memory, Commitment Ordering Figure 1: ACO using Blocking/Stall (BS) and Freeze/Hold (FH) 1. Introduction semantics (of the parallel code) that is equivalent to the original Transactional Memory (TM) [5] is an easy abstraction to program (sequential) code. Regarding the latter, SMR-based transactional concurrent applications. Its integration into main-stream compilers systems order transactions (totally or partially) before their execu- and programming languages such as GCC and C++ gives TM, tion to guarantee that a state always evolves on several computing respectively, accessibility and concreteness. nodes, consistently. To do that, usually a consensus protocol is em- In this poster paper we provide the design of two TM implemen- ployed (e.g., Paxos [6]), which establishes a common order among tations that commit transactions enforcing an order defined prior to transactions. -
Serializability, Not Serial: Concurrency Control and Availability in Multi-Datacenter Datastores
Serializability, not Serial: Concurrency Control and Availability in Multi-Datacenter Datastores Stacy Patterson1 Aaron J. Elmore2 Faisal Nawab2 Divyakant Agrawal2 Amr El Abbadi2 1Department of Electrical Engineering 2Department of Computer Science Technion - Israel Institute of Technology University of California, Santa Barbara Haifa, 32000, Israel Santa Barbara, CA 93106 [email protected] faelmore,nawab,agrawal,[email protected] ABSTRACT create applications within the eventual consistency model We present a framework for concurrency control and avail- [21]. Many cloud providers then introduced support for ability in multi-datacenter datastores. While we consider atomic access to individual data items, in essence, provid- Google's Megastore as our motivating example, we define ing strong consistency guarantees. This consistency level general abstractions for key components, making our solu- has become a standard feature that is offered in most cloud tion extensible to any system that satisfies the abstraction datastore implementations, including BigTable, SimpleDB, properties. We first develop and analyze a transaction man- and Apache HBase [17]. Strong consistency of single data agement and replication protocol based on a straightforward items is sufficient for many applications. However, if several implementation of the Paxos algorithm. Our investigation data items must be updated atomically, the burden to imple- reveals that this protocol acts as a concurrency prevention ment this atomic action in a scalable, fault tolerant manner mechanism rather than a concurrency control mechanism. lies with the software developer. Several recent works have We then propose an enhanced protocol called Paxos with addressed the problem of implementing ACID transactions Combination and Promotion (Paxos-CP) that provides true in cloud datastores [3, 11, 12], and, while full transaction transaction concurrency while requiring the same per in- support remains a scalability challenge, these works demon- stance message complexity as the basic Paxos protocol.