Ensuring performance isolation and differentiation among workloads that share a storage infrastructure is a basic requirement in consolidated data centers. Existing management tools rely on resource provisioning to meet performance goals; they require detailed knowledge of the system characteristics and the workloads. Provisioning is inherently slow to react to system and workload dynamics, and in the general case, it is impossible to provision for the worst case.We propose a software-only solution that ensures predictable performance for storage access. It is applicable to a wide range of storage systems and makes no assumptions about workload characteristics. We use an on-line feedback loop with an adaptive controller that throttles storage access requests to ensure that the available system throughput is shared among workloads according to their performance goals and their relative importance. The controller considers the system as a "black box" and adapts automatically to system and workload changes. The controller is distributed to ensure high availability under overload conditions, and it can be used for both block and file access protocols. The evaluation of Triage, our experimental prototype, demonstrates workload isolation and differentiation, in an overloaded cluster file-system where workloads and system components are changing.

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Pangaea is a wide-area file system that supports data sharing among a community of widely distributed users. It is built on a symmetrically decentralized infrastructure that consists of commodity computers provided by the end users. Computers act autonomously to serve data to their local users. When possible, they exchange data with nearby peers to improve the system's overall performance, availability, and network economy. This approach is realized by aggressively creating a replica of a file whenever and wherever it is accessed.This paper presents the design, implementation, and evaluation of the Pangaea file system. Pangaea offers efficient, randomized algorithms to manage highly dynamic and potentially large groups of file replicas. It applies optimistic consistency semantics to replica contents, but it also offers stronger guarantees when required by the users. The evaluation demonstrates that Pangaea outperforms existing distributed file systems in large heterogeneous environments, typical of the Internet and of large corporate intranets.