Abstract
Protocols like the Direct Access File System (DAFS) leverage user-level memory-mapped communication to enable low overhead access to network-attached storage for applications. DAFS offers significant improvement in application performance using features like direct data transfer and RDMA. Our goal is to build high performance network file servers using DAFS. The benefits of the DAFS protocol can be extended to cluster-based servers, using low overhead user-level communication within the cluster. In this paper, we present Federated DAFS, a scalable and efficient cluster-based direct access file server. Federated DAFS combines an efficient user-space DAFS implementation with a low overhead clustering layer to present a scalable clustering solution for DAFS servers. Federated DAFS uses a portable mechanism for distribution and handling of client requests across the servers in the cluster. Federated DAFS also minimizes the intra-cluster communication by caching data blocks and by matching the file placement on the servers with the distribution of requests from the clients. Our results show that reasonable speedups(2.6 on four nodes and 4.5 on eight nodes) can be achieved using Federated DAFS on server clusters of up to eight nodes.