Using Hysteresis to Reduce Adaptation Cost of a Dynamic Quorum Assignment
01 January 1999
Quorums are a classic decentralized approach to solving coordination problems in distributed computing systems. This work discusses a new method for constructing a dynamic quorum assignment. A dynamic quorum assignment can be adapted during system execution to increase system availability and performance, for example, by removing failed processors from quorums. A method called generalized on-line quorum adaptation is discussed that allows automatic installation of an updated quorum assignment that is computed using any selected quorum mapping function. This general approach enables maximum flexibility in changing the set of quorums that processors can communicate with. The system designer is allowed to make any desired trade-offs between quorum sizes and load, and any number of failed processors can be removed from quorums while the system executes. This work focuses on how the choice of quorum mapping affects the cost of quorum adaptation.