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48
DEPSKY: Dependable and Secure Storage in a Cloud-of-Clouds
, 2013
"... The increasing popularity of cloud storage services has lead companies that handle critical data to think about using these services for their storage needs. Medical record databases, large biomedical datasets, historical information about power systems and financial data are some examples of critic ..."
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Cited by 85 (15 self)
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The increasing popularity of cloud storage services has lead companies that handle critical data to think about using these services for their storage needs. Medical record databases, large biomedical datasets, historical information about power systems and financial data are some examples of critical data that could be moved to the cloud. However, the reliability and security of data stored in the cloud still remain major concerns. In this work we present DEPSKY, a system that improves the availability, integrity and confidentiality of information stored in the cloud through the encryption, encoding and replication of the data on diverse clouds that form a cloud-of-clouds. We deployed our system using four commercial clouds and used PlanetLab to run clients accessing the service from different countries. We observed that our protocols improved the perceived availability and, in most cases, the access latency when compared with cloud providers individually. Moreover, the monetary costs of using DEPSKY on this scenario is at most twice the cost of using a single cloud, which is optimal and seems to be a reasonable cost, given the benefits.
Byzantine disk paxos: optimal resilience with Byzantine shared memory
- Distributed Computing
, 2006
"... We present Byzantine Disk Paxos, an asynchronous sharedmemory consensus protocol that uses a collection of n> 3t disks, t of which may fail by becoming non-responsive or arbitrarily corrupted. We give two constructions of this protocol; that is, we construct two different building blocks, each of ..."
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Cited by 48 (3 self)
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We present Byzantine Disk Paxos, an asynchronous sharedmemory consensus protocol that uses a collection of n> 3t disks, t of which may fail by becoming non-responsive or arbitrarily corrupted. We give two constructions of this protocol; that is, we construct two different building blocks, each of which can be used, along with a leader oracle, to solve consensus. One building block is a shared wait-free safe register. The second building block is a regular register that satisfies a weaker termination (liveness) condition than wait freedom: its write operations are wait-free, whereas its read operations are guaranteed to return only in executions with a finite number of writes. We call this termination condition finite writes (FW), and show that consensus is solvable with FW-terminating registers and a leader oracle. We construct each of these reliable registers from n> 3t base registers, t of which can be non-responsive or Byzantine. All the previous wait-free constructions in this model used at least 4t + 1 fault-prone registers, and we are not familiar with any prior FW-terminating constructions in this model. Categories and Subject Descriptors B.3.2 [Memory Structures]: Design Styles—shared memory; D.4.5 [Operating Systems]: Reliability—fault-tolerance;
Deconstructing paxos
- SIGACT News
"... The Paxos part-time parliament protocol of Lamport provides a very practical way to implement a fault-tolerant deterministic service by replicating it over a distributed message passing system. The contribution of this paper is a faithful deconstruction of Paxos that preserves its efficiency in term ..."
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Cited by 45 (11 self)
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The Paxos part-time parliament protocol of Lamport provides a very practical way to implement a fault-tolerant deterministic service by replicating it over a distributed message passing system. The contribution of this paper is a faithful deconstruction of Paxos that preserves its efficiency in terms of forced logs, messages and communication steps. The key to our faithful deconstruction is the factorisation of the fundamental algorithmic principles of Paxos within two abstractions: weak leader election and round-based consensus, itself based on a round-based register abstraction. Using those abstractions, we show how to reconstruct, in a modular manner, known and new variants of Paxos. In particular, we show how to (1) alleviate the need for forced logs if some processes remain up for sufficiently long, (2) augment the resilience of the algorithm against unstable processes, (3) enable single process decision with shared commodity disks, and (4) reduce the number of communication steps during stable periods of the system.
Paxos At War
- In Proceedings of the 2001 Winter Simulation Conference
, 2004
"... The optimistic latency of Byzantine Paxos can be reduced from three communication steps to two, without using public-key cryptography. This is done by making a decision when more than (n + 3f)/2 acceptors report to have received the same proposal from the leader, with n being the total number of ..."
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Cited by 21 (1 self)
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The optimistic latency of Byzantine Paxos can be reduced from three communication steps to two, without using public-key cryptography. This is done by making a decision when more than (n + 3f)/2 acceptors report to have received the same proposal from the leader, with n being the total number of acceptors and f the number of the faulty ones. No further improvement in latency is possible, because every Consensus algorithm must take at least two steps even in benign settings.
Early-Delivery Dynamic Atomic Broadcast (Extended Abstract)
- IN PROC. 16TH INTL. SYMP. ON DISTRIBUTED COMPUTING (DISC’02), D. MALKHI, ED. LNCS
, 2002
"... We consider a problem of atomic broadcast in a dynamic setting where processes may join, leave voluntarily, or fail (by stopping) during the course of computation. We provide a formal definition of the Dynamic Atomic Broadcast problem and present and analyze a new algorithm for its solution in ..."
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Cited by 19 (3 self)
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We consider a problem of atomic broadcast in a dynamic setting where processes may join, leave voluntarily, or fail (by stopping) during the course of computation. We provide a formal definition of the Dynamic Atomic Broadcast problem and present and analyze a new algorithm for its solution in a variant of a synchronous model, where processes have approximately synchronized clocks. Our
The Alpha of Indulgent Consensus
, 2006
"... This paper presents a simple framework unifying a family of consensus algorithms that can tolerate process crash failures and asynchronous periods of the network, also called indulgent consensus algorithms. Key to the framework is a new abstraction we introduce here, called Alpha, and which precisel ..."
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Cited by 17 (0 self)
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This paper presents a simple framework unifying a family of consensus algorithms that can tolerate process crash failures and asynchronous periods of the network, also called indulgent consensus algorithms. Key to the framework is a new abstraction we introduce here, called Alpha, and which precisely captures consensus safety. Implementations of Alpha in shared memory, storage area network, message passing and active disk systems are presented, leading to directly derived consensus algorithms suited to these communication media. The paper also considers the case where the number of processes is unknown and can be arbitrarily large.
SHARING MEMORY WITH SEMI-BYZANTINE CLIENTS AND FAULTY STORAGE SERVERS
- PARALLEL PROCESSING LETTERS
, 2006
"... This paper presents fault-tolerant simulations of a single-writer multi-reader regular register in storage systems. One simulation tolerates fail-stop failures of storage servers and requires a majority of nonfaulty servers, while the other simulation tolerates Byzantine failures and assumes that tw ..."
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Cited by 12 (1 self)
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This paper presents fault-tolerant simulations of a single-writer multi-reader regular register in storage systems. One simulation tolerates fail-stop failures of storage servers and requires a majority of nonfaulty servers, while the other simulation tolerates Byzantine failures and assumes that two-thirds of the servers are nonfaulty. A construction of Afek et al. [3] is used to mask semi-Byzantine failures of clients that result in erroneous write operations. The simulations are used to derive Paxos algorithms that tolerate semi-Byzantine failures of clients as well as fail-stop or Byzantine failures of storage servers.
Robust Data Sharing with Key-Value Stores
"... A key-value store (KVS) offers functions for storing and retrieving values associated with unique keys. KVSs have become the most popular way to access Internet-scale “cloud” storage systems. We present an efficient wait-free algorithm that emulates multi-reader multi-writer storage from a set of po ..."
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Cited by 10 (1 self)
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A key-value store (KVS) offers functions for storing and retrieving values associated with unique keys. KVSs have become the most popular way to access Internet-scale “cloud” storage systems. We present an efficient wait-free algorithm that emulates multi-reader multi-writer storage from a set of potentially faulty KVS replicas in an asynchronous environment. Our implementation serves an unbounded number of clients that use the storage concurrently. It tolerates crashes of a minority of the KVSs and crashes of any number of clients. Our algorithm minimizes the space overhead at the KVSs and comes in two variants providing regular and atomic semantics, respectively. Compared with prior solutions, it is inherently scalable and allows clients to write concurrently. Because of the limited interface of a KVS, textbook-style solutions for reliable storage either do not work or incur a prohibitively large storage overhead. Our algorithm maintains two copies of the stored value per KVS in the common case, and we show that this is indeed necessary. If there are concurrent write operations, the maximum space complexity of the algorithm grows in proportion to the point contention. A series of simulations explore the behavior of the algorithm, and benchmarks obtained with KVS cloud-storage providers demonstrate its practicality.
Wait-free regular storage from byzantine components
- INFORMATION PROCESSING LETTERS (IPL
, 2006
"... We consider the problem of implementing a wait-free regular register from storage components prone to Byzantine faults. We present a simple, efficient, and self-contained construction of such a register. Our construction utilizes a novel building block, called a 1-regular register, which can be eff ..."
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Cited by 9 (1 self)
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We consider the problem of implementing a wait-free regular register from storage components prone to Byzantine faults. We present a simple, efficient, and self-contained construction of such a register. Our construction utilizes a novel building block, called a 1-regular register, which can be efficiently implemented from Byzantine fault-prone components.
