Towards a Globalised Data Access

Abstract

In this chapter we address various solutions to initiate a smooth transition from a high performance storage model composed by several nodes in different distant sites to a model where the nodes cooperate to give a unique file system-like coherent view of their content. This task, historically considered very problematic, has to be considered from several points of view, functional and not, in order to be able to deploy a production-quality system, where the functionalities are effectively usable, and the data access performance is as close as possible to the one reachable by the used hardware. This can be considered as the major challenge in such systems, even because the general expectations about performance and robustness are very high, and very often they are compared to distributed file systems, whose evolution over time has been quite promising, but not to the point of being able to fully satisfy the requirements of large scale computing. To reach this objective, among other items, a design must face the difficulties dealing with the network latency, which varies of more than two orders of magnitude between local network access and Wide Area Network access.