Model of QoS Management in a Distributed Data Sharing and Archiving System.

The scientific applications of the fourth paradigm of science deal with large amounts of data stored in various storage devices or systems. Distributed storage systems are often chosen for storing these data. Some of the requirements posed to those storage systems may concern Quality of Service (QoS) aspects formally expressed in a Service Level Agreement. The QoS management in distributed storage systems is a challenging task given the possible storage device heterogeneity, the dynami- cally changing data access patterns, the client's concurrency and storage resource sharing. The problem becomes even more complicated when distributed computing environments with virtualized and shared resources like Clouds are considered. In this paper we present our research concerning the methods of storage performance management with respect of QoS in dis- tributed environments which has been done within the National Data Storage 2 (NDS2) project. A new model of storage QoS management is proposed and its implementation within NDS2 is described.