Consistability: Describing Usually Consistent Systems

Current weak consistency semantics provide worst-case guarantees to clients. These guarantees fail to adequately describe systems that provide varying levels of consistency in the face of distinct failure modes, or that achieve better than worst-case guarantees during normal execution. The inability to make precise statements about consistency throughout a system's execution represents a lost opportunity to clearly understand client application requirements and to optimize systems and services appropriately. In this position paper, we motivate the need for and introduce the concept of consistability--a unified metric of consistency and availability. Consistability offers a means of describing, specifying, and discussing how much consistency a usually consistent system provides, and how often it does so. We describe our initial results of applying consistability reasoning to a keyvalue store we are developing and to other recent distributed systems. We also discuss the limitations...

• Type: Conference
• Year: 2008
• Where: HOTDEP
• Authors: Amitanand S. Aiyer, Eric Anderson, Xiaozhou Li, Mehul A. Shah, Jay J. Wylie
• Keywords: Consistency, Hardware, HOTDEP 2008, Weak Consistency Semantics, Worst-case Guarantees