Results 1 - 10 of 511

Dynamo: amazon’s highly available key-value store

by Giuseppe DeCandia, Deniz Hastorun, Madan Jampani, Gunavardhan Kakulapati, Avinash Lakshman, Alex Pilchin, Swaminathan Sivasubramanian, Peter Vosshall, Werner Vogels - IN PROC. SOSP , 2007
"... Reliability at massive scale is one of the biggest challenges we face at Amazon.com, one of the largest e-commerce operations in the world; even the slightest outage has significant financial consequences and impacts customer trust. The Amazon.com platform, which provides services for many web sites ..."
Abstract - Cited by 684 (0 self) - Add to MetaCart
Reliability at massive scale is one of the biggest challenges we face at Amazon.com, one of the largest e-commerce operations in the world; even the slightest outage has significant financial consequences and impacts customer trust. The Amazon.com platform, which provides services for many web sites worldwide, is implemented on top of an infrastructure of tens of thousands of servers and network components located in many datacenters around the world. At this scale, small and large components fail continuously and the way persistent state is managed in the face of these failures drives the reliability and scalability of the software systems. This paper presents the design and implementation of Dynamo, a highly available key-value storage system that some of Amazon’s core services use to provide an “always-on ” experience. To achieve this level of availability, Dynamo sacrifices consistency under certain failure scenarios. It makes extensive use of object versioning and application-assisted conflict resolution in a manner that provides a novel interface for developers to use.
(Show Context)

Agile Application-Aware Adaptation for Mobility

by Brian D. Noble, M. Satyanarayanan, Dushyanth Narayanan, James Eric Tilton, Jason Flinn, Kevin R. Walker - SOSP-16 , 1997
"... In this paper we show that application-aware adaptation, a collaborative partnership between the operating system and applications, offers the most general and effective approach to mobile information access. We describe the design of Odyssey, a prototype implementing this approach, and show how it ..."
Abstract - Cited by 507 (32 self) - Add to MetaCart
In this paper we show that application-aware adaptation, a collaborative partnership between the operating system and applications, offers the most general and effective approach to mobile information access. We describe the design of Odyssey, a prototype implementing this approach, and show how it supports concurrent execution of diverse mobile applications. We identify agility as a key attribute of adaptive systems, and describe how to quantify and measure it. We present the results of our evaluation of Odyssey, indicating performance improvements up to a factor of 5 on a benchmark of three applications concurrently using remote services over a network with highly variable bandwidth.
(Show Context)

Cassandra- A Decentralized Structured Storage System

by Avinash Lakshman, Prashant Malik
"... Cassandra is a distributed storage system for managing very large amounts of structured data spread out across many commodity servers, while providing highly available service with no single point of failure. Cassandra aims to run on top of an infrastructure of hundreds of nodes (possibly spread acr ..."
Abstract - Cited by 360 (0 self) - Add to MetaCart
Cassandra is a distributed storage system for managing very large amounts of structured data spread out across many commodity servers, while providing highly available service with no single point of failure. Cassandra aims to run on top of an infrastructure of hundreds of nodes (possibly spread across different data centers). At this scale, small and large components fail continuously. The way Cassandra manages the persistent state in the face of these failures drives the reliability and scalability of the software systems relying on this service. While in many ways Cassandra resembles a database and shares many design and implementation strategies therewith, Cassandra does not support a full relational data model; instead, it provides clients with a simple data model that supports dynamic control over data layout and format. Cassandra system was designed to run on cheap commodity hardware and handle high write throughput while not sacrificing read efficiency. 1.
(Show Context)

Epidemic routing for partially-connected ad hoc networks

by Amin Vahdat, David Becker , 2000
"... Mobile ad hoc routing protocols allow nodes with wireless adaptors to communicate with one another without any pre-existing network infrastructure. Existing ad hoc routing protocols, while robust to rapidly changing network topology, assume the presence of a connected path from source to destination ..."
Abstract - Cited by 358 (0 self) - Add to MetaCart
Mobile ad hoc routing protocols allow nodes with wireless adaptors to communicate with one another without any pre-existing network infrastructure. Existing ad hoc routing protocols, while robust to rapidly changing network topology, assume the presence of a connected path from source to destination. Given power limitations, the advent of short-range wireless networks, and the wide physical conditions over which ad hoc networks must be deployed, in some scenarios it is likely that this assumption is invalid. In this work, we develop techniques to deliver messages in the case where there is never a connected path from source to destination or when a network partition exists at the time a message is originated. To this end, we introduce Epidemic Routing, where random pair-wise exchanges of messages among mobile hosts ensure eventual message delivery. The goals of Epidemic Routing are to: i) maximize message delivery rate, ii) minimize message latency, and iii) minimize the total resources consumed in message delivery. Through an implementation in the Monarch simulator, we show that Epidemic Routing achieves eventual delivery of 100 % of messages with reasonable aggregate resource consumption in a number of interesting scenarios. 1
(Show Context)

Flexible Update Propagation for Weakly Consistent Replication

by Karin Petersen, Mike J. Spreitzer , Douglas B. Terry , Marvin M. Theimer, Alan J. Demers
"... Bayou’s anti-entropy protocol for update propagation between weakly consistent storage replicas is based on pair-wise communication, the propagation of write operations, and a set of ordering and closure constraints on the propagation of the writes. The simplicity of the design makes the protocol ve ..."
Abstract - Cited by 327 (11 self) - Add to MetaCart
Bayou’s anti-entropy protocol for update propagation between weakly consistent storage replicas is based on pair-wise communication, the propagation of write operations, and a set of ordering and closure constraints on the propagation of the writes. The simplicity of the design makes the protocol very flexible, thereby providing support for diverse networking environments and usage scenarios. It accommodates a variety of policies for when and where to propagate updates. It operates over diverse network topologies, including low-bandwidth links. It is incremental. It enables replica convergence, and updates can be propagated using floppy disks and similar transportable media. Moreover, the protocol handles replica creation and retirement in a light-weight manner. Each of these features is enabled by only one or two of the protocol’s design choices, and can be independently incorporated in other systems. This paper presents the antientropy protocol in detail, describing the design decisions and resulting features.

Ivy: A Read/Write Peer-to-Peer File System

by Athicha Muthitacharoen, Robert Morris, Thomer M. Gil, Benjie Chen , 2002
"... Ivy is a multi-user read/write peer-to-peer file system. Ivy has no centralized or dedicated components, and it provides useful integrity properties without requiring users to fully trust either the underlying peer-to-peer storage system or the other users of the file system. An Ivy file system con ..."
Abstract - Cited by 298 (12 self) - Add to MetaCart
Ivy is a multi-user read/write peer-to-peer file system. Ivy has no centralized or dedicated components, and it provides useful integrity properties without requiring users to fully trust either the underlying peer-to-peer storage system or the other users of the file system. An Ivy file system consists solely of a set of logs, one log per participant. Ivy stores its logs in the DHash distributed hash table. Each participant finds data by consulting all logs, but performs modifications by appending only to its own log. This arrangement allows Ivy to maintain meta-data consistency without locking. Ivy users can choose which other logs to trust, an appropriate arrangement in a semi-open peer-to-peer system. Ivy presents applications with a conventional file system interface. When the underlying network is fully connected, Ivy provides NFS-like semantics, such as close-to-open consistency. Ivy detects conflicting modifications made during a partition, and provides relevant version information to application-specific conflict resolvers. Performance measurements on a wide-area network show that Ivy is two to three times slower than NFS.
(Show Context)

Optimistic replication

by Yasushi Saito, Marc Shapiro - ACM COMPUTING SURVEYS , 2005
"... Data replication is a key technology in distributed data sharing systems, enabling higher availability and performance. This paper surveys optimistic replication algorithms that allow replica contents to diverge in the short term, in order to support concurrent work practices and to tolerate failure ..."
Abstract - Cited by 290 (19 self) - Add to MetaCart
Data replication is a key technology in distributed data sharing systems, enabling higher availability and performance. This paper surveys optimistic replication algorithms that allow replica contents to diverge in the short term, in order to support concurrent work practices and to tolerate failures in low-quality communication links. The importance of such techniques is increasing as collaboration through wide-area and mobile networks becomes popular. Optimistic replication techniques are different from traditional “pessimistic” ones. Instead of synchronous replica coordination, an optimistic algorithm propagates changes in the background, discovers conflicts after they happen and reaches agreement on the final contents incrementally. We explore the solution space for optimistic replication algorithms. This paper identifies key challenges facing optimistic replication systems — ordering operations, detecting and resolving conflicts, propagating changes efficiently, and bounding replica divergence — and provides a comprehensive survey of techniques developed for addressing these challenges.

Design and Evaluation of a Continuous Consistency Model for Replicated Services

by Haifeng Yu , Amin Vahdat , 2000
"... The tradeoffs between consistency, performance, and availability are well understood. Traditionally, however, designers of replicated systems have been forced to choose from either strong consistency guarantees or none at all. This paper explores the semantic space between traditional strong and opt ..."
Abstract - Cited by 190 (13 self) - Add to MetaCart
The tradeoffs between consistency, performance, and availability are well understood. Traditionally, however, designers of replicated systems have been forced to choose from either strong consistency guarantees or none at all. This paper explores the semantic space between traditional strong and optimistic consistency models for replicated services. We argue that an important class of applications can tolerate relaxed consistency, but benefit from bounding the maximum rate of inconsistent access in an application-specific manner. Thus, we develop a set of metrics, Numerical Error, Order Error, and Staleness, to capture the consistency spectrum. We then present the design and implementation of TACT, a middleware layer that enforces arbitrary consistency bounds among replicas using these metrics. Finally, we show that three replicated applications demonstrate significant semantic and performance benefits from using our framework.

Carisma: context-aware reflective middleware system for mobile applications

by Licia Capra, Wolfgang Emmerich, Cecilia Mascolo - IEEE TRANS. ON SOFTWARE ENGINEERING , 2003
"... Mobile devices, such as mobile phones and personal digital assistants, have gained wide-spread popularity. These devices will increasingly be networked, thus enabling the construction of distributed applications that have to adapt to changes in context, such as variations in network bandwidth, batt ..."
Abstract - Cited by 177 (5 self) - Add to MetaCart
Mobile devices, such as mobile phones and personal digital assistants, have gained wide-spread popularity. These devices will increasingly be networked, thus enabling the construction of distributed applications that have to adapt to changes in context, such as variations in network bandwidth, battery power, connectivity, reachability of services and hosts, etc. In this paper, we describe CARISMA, a mobile computing middleware which exploits the principle of reflection to enhance the construction of adaptive and context-aware mobile applications. The middleware provides software engineers with primitives to describe how context changes should be handled using policies. These policies may conflict. We classify the different types of conflicts that may arise in mobile computing and argue that conflicts cannot be resolved statically at the time applications are designed, but, rather, need to be resolved at execution time. We demonstrate a method by which policy conflicts can be handled; this method uses a microeconomic approach that relies on a particular type of sealed-bid auction. We describe how this method is implemented in the CARISMA middleware architecture and sketch a distributed context-aware application for mobile devices to illustrate how the method works in practice. We show, by way of a systematic performance evaluation, that conflict resolution does not imply undue overheads, before comparing our research to related work and concluding the paper.
(Show Context)

Onix: a distributed control platform for large-scale production networks.

by Teemu Koponen , Martin Casado , Natasha Gude , Jeremy Stribling , Leon Poutievski , Min Zhu , Rajiv Ramanathan , Yuichiro Iwata , Hiroaki Inoue , Takayuki Hama , Scott Shenker - In USENIX OSDI, , 2010
"... Abstract Computer networks lack a general control paradigm, as traditional networks do not provide any networkwide management abstractions. As a result, each new function (such as routing) must provide its own state distribution, element discovery, and failure recovery mechanisms. We believe this l ..."
Abstract - Cited by 164 (10 self) - Add to MetaCart
Abstract Computer networks lack a general control paradigm, as traditional networks do not provide any networkwide management abstractions. As a result, each new function (such as routing) must provide its own state distribution, element discovery, and failure recovery mechanisms. We believe this lack of a common control platform has significantly hindered the development of flexible, reliable and feature-rich network control planes. To address this, we present Onix, a platform on top of which a network control plane can be implemented as a distributed system. Control planes written within Onix operate on a global view of the network, and use basic state distribution primitives provided by the platform. Thus Onix provides a general API for control plane implementations, while allowing them to make their own trade-offs among consistency, durability, and scalability.
(Show Context)