| 1. |
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| 2. |
- Arad, Cosmin, et al.
(författare)
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CATS: linearizability and partition tolerance in scalable and self-organizing key-value stores
- 2012. - 7
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Distributed key-value stores provide scalable, fault-tolerant, and self-organizing storage services, but fall short of guaranteeing linearizable consistency in partially synchronous, lossy, partitionable, and dynamic networks, when data is distributed and replicated automatically by the principle of consistent hashing. This paper introduces consistent quorums as a solution for achieving atomic consistency. We present the design and implementation of CATS, a distributed key-value store which uses consistent quorums to guarantee linearizability and partition tolerance in such adverse and dynamic network conditions. CATS is scalable, elastic, and self-organizing; key properties for modern cloud storage middleware. Our system shows that consistency can be achieved with practical performance and modest throughput overhead (5%) for read-intensive workloads.
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| 3. |
- Shafaat, Tallat M., et al.
(författare)
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A method of adaptive coarsening for compressing scientific datasets
- 2007
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Ingår i: Applied Parallel Computing. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783540757542 ; , s. 774-780
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Konferensbidrag (refereegranskat)abstract
- We present adaptive coarsening, a multi-resolution lossy compression algorithm for scientific datasets. The algorithm provides guaranteed error bounds according to the user's requirements for subsequent post-processing. We demonstrate compression factors of up to an order of magnitude with datasets coming from solutions to time-dependent partial differential equations in one and two dimensions.
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| 4. |
- Shafaat, Tallat M., et al.
(författare)
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A Practical Approach to Network Size Estimation for Structured Overlays
- 2008
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Ingår i: SELF-ORGANIZING SYSTEMS, PROCEEDINGS. - Berlin : SPRINGER-VERLAG. - 9783540921561 ; , s. 71-83
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Konferensbidrag (refereegranskat)abstract
- Structured overlay networks have recently received much attention due to their self-* properties under dynamic and decentralized settings. The number of nodes in all overlay fluctuates all the time due to churn. Since knowledge of the size of the. overlay is a core requirement for many systems, estimating the size in a decentralized manner is a challenge taken up by recent research activities. Gossip-based Aggregation has been shown to give accurate estimates for the network size, but previous work done is highly sensitive to node failures. In this paper, we present a gossip-based aggregation-style network size estimation algorithm. We discuss shortcomings of existing aggregation-based size estimation algorithms, and give a solution that is highly robust to node failures and is adaptive to network delays. We examine our solution in various scenarios to demonstrate. its effectiveness.
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| 5. |
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| 6. |
- Shafaat, Tallat M., et al.
(författare)
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Dealing with network partitions in structured overlay networks
- 2009
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Ingår i: Peer-to-Peer Networking and Applications. - : Springer Science and Business Media LLC. - 1936-6442 .- 1936-6450. ; 2:4, s. 334-347
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Tidskriftsartikel (refereegranskat)abstract
- Structured overlay networks form a major class of peer-to-peer systems, which are touted for their abilities to scale, tolerate failures, and self-manage. Any long-lived Internet-scale distributed system is destined to face network partitions. Although the problem of network partitions and mergers is highly related to fault-tolerance and self-management in large-scale systems, it has hardly been studied in the context of structured peer-to-peer systems. These systems have mainly been studied under churn (frequent joins/failures), which as a side effect solves the problem of network partitions, as it is similar to massive node failures. Yet, the crucial aspect of network mergers has been ignored. In fact, it has been claimed that ring-based structured overlay networks, which constitute the majority of the structured overlays, are intrinsically ill-suited for merging rings. In this paper, we present an algorithm for merging multiple similar ring-based overlays when the underlying network merges. We examine the solution in dynamic conditions, showing how our solution is resilient to churn during the merger, something widely believed to be difficult or impossible. We evaluate the algorithm for various scenarios and show that even when falsely detecting a merger, the algorithm quickly terminates and does not clutter the network with many messages. The algorithm is flexible as the tradeoff between message complexity and time complexity can be adjusted by a parameter.
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| 7. |
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| 8. |
- Shafaat, Tallat M., et al.
(författare)
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Handling network partitions and mergers in structured overlay networks
- 2007
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Ingår i: P2P. - 9780769529868 ; , s. 132-139
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Konferensbidrag (refereegranskat)abstract
- Structured overlay networks form a major class of peer-to-peer systems, which are touted for their abilities to scale, tolerate failures, and self-manage. Any long-lived Internet-scale. distributed system is destined to face network partitions. Although the problem of network partitions and mergers is highly related to fault-tolerance and self-management in large-scale systems, it has hardly been studied in the context of structured peer-to-peer systems. These systems have mainly been studied under chum (frequent joins/failures), which as a side effect solves the problem of network partitions, as it is similar to massive node failures. Yet, the crucial aspect of network mergers has been ignored. In fact, it has been claimed that ring-based structured overlay networks, which constitute the majority of the structured overlays, are intrinsically ill-suited for merging rings. In this paper we present an algorithm for merging multiple similar ring-based overlays when the underlying network merges. We examine the solution in dynamic conditions, showing how our solution is resilient to churn during the merger something widely believed to be difficult or impossible. We evaluate the algorithm for various scenarios and show that even when falsely detecting a merger the algorithm quickly terminates and does not clutter the network with many messages. The algorithm is flexible as the tradeoff between message complexity and time complexity can be adjusted by a parameter.
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| 9. |
- Shafaat, Tallat M., et al.
(författare)
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ID-replication for structured peer-to-peer systems
- 2012
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Ingår i: Euro-Par 2012 Parallel Processing. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642328190 ; , s. 364-376
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Konferensbidrag (refereegranskat)abstract
- Structured overlay networks, like any distributed system, use replication to avoid losing data in the presence of failures. In this paper, we discuss the short-comings of existing replication schemes and propose a technique for replication, called ID-Replication. ID-Replication allows different replication degrees for keys in the system, thus allowing popular data to have more copies. We discuss how ID-Replication is less sensitive to churn compared to existing replication schemes, which makes ID-Replication better suited for building consistent services on top of overlays compared to other schemes. Furthermore, we show why ID-Replication is simpler to load-balance and more secure compared to successor-list replication. We evaluate our scheme in detail, and compare it with successor-list replication.
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| 10. |
- Shafaat, Tallat M., et al.
(författare)
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Key-based consistency and availability in structured Overlay Networks
- 2008
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Ingår i: Proceedings of the 17th International Symposium on High Performance Distributed Computing 2008, HPDC'08. - New York, NY, USA : ACM. - 9781595939975 ; , s. 235-236
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Konferensbidrag (refereegranskat)abstract
- Structured Overlay Networks (SONs) provide a promising platform for high performance applications since they are scalable, fault-tolerant and self-managing. SONs provide lookup services that map keys to nodes that can be used as processing or storage resources. In SONs, lookups for a key may return inconsistent results. Consequently, it is difficult to provide consistent data services on top of SONs that build on key-based search. In this paper, we study the frequency of occurrence of inconsistent lookups. We show that the affect of lookup inconsistencies can be reduced by using node responsibilities. We present our results as a trade-off between consistency and availability of keys.
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