D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Transactions on Computers, 36:1197--1208, October 1987.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....(e.g. probabilistic broadcast [12] is indeed an option, yet the incurred overhead is not low enough to address a broad application context. A more drastic shift seems to be necessary. Such a step has been initiated (again first in wired networks) through the introduction of quorum systems [13]. This approach improves the e#ciency of the replication of the stored data by better balancing the load between updates and queries. A quorum system is, roughly, a set of quorums, each consisting of a subset of server replicas. By ensuring that the intersections of quorums meet certain ....

D. Barbara and H. Garcia-Molina, "The reliability of vote mechanisms," IEEE Trans. on Computers, vol. 36, no. 10, pp. 1197--1208, 1987.

....to define the quorums. Each processor has a number of votes, and a quorum is any set of processors with a combined number of votes exceeding half of the system s total number of votes. The simple majority system is the most obvious voting system. The availability of voting systems is studied in [4]. It is shown that in terms of availability, the majority is the best quorum system when p 2 . In [35] the failure probability function F p is characterized, and among other things it is shown that the singleton has the best availability when p 2 . The case when the elements fail with ....

D. Barbara and H. Garcia-Molina, The reliability of vote mechanisms, IEEE Trans. Comput. , C-36 (1987), pp. 1197--1208.

....Compared with performing every operation at every server, using quorums reduces the load on servers and increases service availability despite server crashes. Quorum systems are traditionally assessed by three measures of quality: load [34] fault tolerance [4] and failure probability (see [5, 35]) The load of a quorum system is a measure of its eciency: it is the rate at which the busiest server is accessed. The fault tolerance of a system is the maximum number of server failures for which there is still guaranteed to be a quorum containing no faulty servers. The failure probability is ....

....using probabilistic quorum constructions can be driven further toward zero when updates are suciently dispersed in time, making probabilistic quorum constructions useful in a wider variety of settings. 1.2. Related work Strict quorum systems have been extensively studied and measured (cf. [17, 40, 26, 16, 20, 5, 14, 10, 1, 34, 37, 35]) Byzantine quorum systems were introduced in [29] and further studied in [31, 8] Because of the possibility of inconsistency admitted by probabilistic quorum systems, they are most attractive for systems in which some level of inconsistency can be tolerated, and in particular, where the ....

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D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Transactions on Computers, C-36:1197-1208, October 1987.

....to define the quorums. Each processor has a number of votes, and a quorum is any set of processors with a combined number of votes exceeding half of the system s total number of votes. The simple majority system is the most obvious voting system. The availability of voting systems is studied in [4]. It is shown that in terms of availability, the majority is the best quorum system when p 1 2 . In [33] the failure probability function F p is characterized, and among other things it is shown that the singleton has the best availability when p 1 2 . The case when the elements fail ....

D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Trans. Comput., C-36:1197--1208, October 1987.

....from its lock) will be denied permission by at least one member of any quorum it chooses to access. 1. 2 Overview It is known that when all of the processors have the same independent failure probability p then the optimal availability quorum system is either the Majority system if p 1=2 [BG87] or the Monarchy if p 1=2 [PW95, DKK 94] If the failure probabilities p i are different and all less than 1 2, then the optimal availability quorum system is known to be defined by voting. If 0 p i 1 2 for all i then [TK88] and [SB94] show that the optimal weights are defined by the ....

D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Trans. Comput., C-36:1197--1208, October 1987.

....to define the quorums. Each processor has a number of votes, and a quorum is any set of processors with a combined number of votes exceeding half of the system s total number of votes. The simple majority system is the most obvious voting system. The availability of voting systems is studied in [BG87] It is shown that in terms of availability, the majority is the best quorum system when p 1 2 . In [PW93] the failure probability function F p is characterized, and among other things it is shown that the singleton has the best availability when p 1 2 . The case when the elements fail with ....

D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Trans. Comput., C-36:1197--1208, October 1987.

....to define the quorums. Each processor has a number of votes, and a quorum is any set of processors with a combined number of votes exceeding half of the system s total number of votes. The simple majority system is the most obvious voting system. The availability of voting systems is studied in [4]. It is shown that in terms of availability, the majority is the best quorum system when p 1 2 . In [35] the failure probability function F p is characterized, and among other things it is shown that the singleton has the best availability when p 1 2 . The case when the elements fail with ....

D. Barbara and H. Garcia-Molina, The reliability of vote mechanisms, IEEE Trans. Comput., C-36 (1987), pp. 1197--1208.

....Optimal for f resilient systems. z e.g. ff = 0:5 and fi = 0:21 for RT(4; 3) Table 1: Constructions in this paper (n = number of servers) 2 Related work Our work borrows from prior work in benignly fault tolerant quorum systems, which is extensive (e.g. Gif79, Tho79, Mae85, GB85, Her86, BG87, ET89, AE91, CAA92, NW94, PW97b] The notion of availability we use here (crash probability) is well known in reliability theory [BP75] and has been applied extensively in the analysis of quorum systems (cf. BG87, PW95, PW97a] and the references therein) The load of a quorum system was first ....

.... quorum systems, which is extensive (e.g. Gif79, Tho79, Mae85, GB85, Her86, BG87, ET89, AE91, CAA92, NW94, PW97b] The notion of availability we use here (crash probability) is well known in reliability theory [BP75] and has been applied extensively in the analysis of quorum systems (cf. BG87, PW95, PW97a] and the references therein) The load of a quorum system was first defined and analyzed in [NW94] which proved a lower bound of Omega Gamma 1 p n ) on the load of any quorum system (and, a fortiori, any masking quorum system) over n servers. In proving load optimality of our ....

D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Trans. Comput., C-36:1197--1208, October 1987. -- --

....such as independent failures and perfect communication are made to render the problem tractable. The results of this approach are rigorous and definitive. Analyses of the availability (probability that a live quorum exists in the system) assuming a complete and fault free network, can be found in [8, 34, 12, 37, 7]. Analyses of the expected size of a connected component containing a quorum, and the availability on ring networks are [32, 19] An analysis of the load can be found in [29, 18] A queuing system analysis is [26] ffl Simulation: In this approach (cf. 21, 14, 24] a simulation model is ....

....in measures that quantify the quality of service that a particular quorum system provides. A basic notion in these measures is that of a live quorum: a quorum is called alive when all its processors are alive. The measures we consider are: UnAvail: This is the un availability of the system [8], the probability of the event that no live quorum exists in the system. When such an event occurs the service is completely halted. The un availability is widely accepted as the measure by which quorum systems are evaluated. AvgUnAcc: Another appropriate measure [22] is the unaccessibility UA i ....

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D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Trans. Comput., C-36:1197--1208, Oct. 1987.

....masking quorum system that demonstrate that our construction is asymptotically load optimal when b = p n) 1 Note that this also demonstrates the tightness of our lower bounds in this case. We also show that our construction offers good availability by studying its failure probability [BG87, PW95]. Even when designed with Byzantine failures in mind, an important property of a replication scheme is the extent to which it can ensure data availability in the face of benign server failures (crashes) Failure probability, which measures such availability, is the probability that the system ....

....over strict systems is best demonstrated by precise failure probability comparisons, rather than by asymptotic bounds. Figure 1 shows this comparison for some values of n and b. The left side of Figure 1 compares F p (R k (n; q) to the lower bound on failure probability for any strict system [BG87, PW95]. 2 This figure shows that our construction can beat this lower bound and hence the failure probability of any strict system for many values of p in settings where b = p n. This comparison is further pronounced in the right side of Figure 1, where our construction is directly compared to ....

D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Trans. Comput., C-36:1197-- 1208, October 1987.

....probability for b masking quorum systems and introduce quorum composition. In Sections 5 7 we describe our new constructions. We conclude in Section 8. 2 Related work Our work borrows from extensive prior work in benignly fault tolerant quorum systems (e.g. Gif79, Tho79, Mae85, GB85, Her86, BG87, ET89, AE91, CAA92, NW94, PW97b] The notion of availability we use here (crash probability) is well known in reliability theory [BP75] and has been applied extensively in the analysis of quorum systems (cf. BG87, PW95, PW97a] and the references therein) The load of a quorum system was first ....

.... in benignly fault tolerant quorum systems (e.g. Gif79, Tho79, Mae85, GB85, Her86, BG87, ET89, AE91, CAA92, NW94, PW97b] The notion of availability we use here (crash probability) is well known in reliability theory [BP75] and has been applied extensively in the analysis of quorum systems (cf. BG87, PW95, PW97a] and the references therein) The load of a quorum system was first defined and analyzed in [NW94] which proved a lower bound of Omega Gamma 1 p n ) on the load of any quorum system (and, a fortiori, any masking quorum system) over n servers. In proving load optimality of our ....

D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Trans. Comput., C-36:1197-- 1208, October 1987.

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D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Transactions on Computers, 36:1197--1208, October 1987.

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D. Barbara and H. Garcia-Molina, "The Reliability of Vote Mechanisms," IEEE Trans. Computers, vol. 36, no. 10, pp. 11971.

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D. Barbara and H. Garcia-Molina, "The reliability of vote mechanisms," IEEE Trans. on Computers, vol. 36, no. 10, pp. 1197--1208, 1987.

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D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Transactions on Computers, 36:1197--1208, October 1987.

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D. Barbara and H. Garcia-Molina. The reliability of vote mechanisms. IEEE Transactions on Computers, 36:1197--1208, October 1987.

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