1 Presentation at SciDAC face-to-face January 2005 Ron A. Oldfield Sandia National Laboratories The Lightweight File System

2 The Lightweight File System Project Participants: –SNL: Ward, Oldfield, Riesen, Lawry –UNM: Maccabe, Arunagiri Motivation –Risk-mitigation for Red Storm PFS (Lustre) –Vehicle for parallel I/O research Design Goals –Lightweight design only critical I/O functionality (direct access to storage, security) special functionality implemented in I/O libraries (above LWFS) –Scalable expect clients with tens-to-hundreds of thousands of processes I/O system should not hinder scalability of the application –Secure authentication and authorization fine-grained access controls with revocation An experimental object-based storage system (funded by Sandia’s CS research foundation)

3 Key features of LWFS Initial focus is on “secure storage architecture” (not a file system) Policy vs mechanism –Separate policy decisions from policy enforcement –Metadata servers and storage servers cooperate for policy consistency Access-control –capability-based –immediate revocation –automatic refresh –fine-grained operation control Containers for related objects –the unit for access control (no control for byte, object, or block access) –Every object is in a container –LWFS knows nothing about the structure of container –We have backwards pointers (not forwards)

4 What LWFS does not do naming (e.g, metadata) data synchronization data consistency caching prefetching quota enforcement data distribution

5 Basic LWFS Architecture Security model (Authentication and Authorization) –Separation of policy from mechanism –Scalable No connection-based mechanisms (e.g., Kerberos) –Capabilities for access control (well... not quite) not independently verifiable Similar to the NASD access credential –Coarse-grained access control (containers) Storage service –object-based –enforcement of access control policies

6 Security Assumptions and Requirements We assume a trusted transport mechanism –prevents replay attacks, man-in-the-middle attacks, and eavesdropping –provides network integrity –We do not need to provide encryption Authentication –Use existing mechanisms (e.g., Kerberos, GSS-API) –Scalable (no connection-based schemes) Authorization –Coarse grained access controls (at the container level) –Capabilities for scalability –“Immediate” revocation of capabilities Integrity –Make sure users cannot modify capabilities

7 Understanding the Scalability Requirements Prohibit ops with O(n) communications Prohibit data structures of size O(n) Limit ops with O(m) comms to rare events The I/O system should not hinder scalability of application

8 Motivating the “Open-Architecture” Model Application-specific APIs –MPI-IO –HDF5, PnetCDF –ChemIO, SalvoIO Application control of policies –Caching and prefetching –Data distribution –Synchronization Applications should choose nearly all features of the I/O system application LWFS access to datasets, app-specific APIs, caching, prefetching high-level I/O lib acesss to (parallel) files, reliability, data distribution, consistency, synchronization access to bytes (in objects), metadata management, security traditional PFS low-level I/O lib

9 Status APIs defined –Storage service –Authentication and Authorization –Naming service –Transactions (Locks and Journals) Prototype implementations –Storage service –Authorization service –Naming service (in progress)

10 Current and Future Work Vehicle for parallel I/O research –Scalable metadata –Application-specific I/O libs and file systems data distribution, data consistency, caching, prefetching to match access patterns mobile app/lib code (e.g., active disk) –Lock-free synchronization schemes –Lightweight database (using LWFS) Framework for developing production-level parallel I/O systems