NeST: Network storage

1. NeST: Network StorageJohn Bent, Venkateshwaran VMiron Livny, Andrea Arpaci-Dusseau, Remzi Arpaci-Dusseau

2. NeST: Network storage • Flexible, commodity based, software-only storage appliances • A storage appliance must be • easy to deploy • self-configurable to minimize administrative costs • reliable but also recoverable • secure against intrusion yet transparent to legit users

3. From commodity to appliance • Why build appliance on commodity system? • Want to ride commodity cost curve • Avoid high cost of specialized servers (e.g. NetApp) • Leverage high availability of commodity systems • Allow on-demand acquisition and deployment • Challenge of building on commodity systems • Must be portable across multiple operating systems • Additional challenge to achieve high performance at user level • Must be adaptable across a range of storage devices

4. NeST structure • Protocol layer • Pluggable protocols map diverse protocols into common control flows • Analogous to Linux v-nodes • Transfer layer • Different concurrency architectures maximize system throughput across diverse platforms • Storage layer • Provides abstract interface to disks and memory

5. GFTP NeST WiND HTTP NFS Protocol Layer NeST Structure Control Logic Concurrency Architecture Pool of processes Pool of threads Nonblocking Storage Layer Raw disk Local FS RAID Memory

6. Many Protocols, Single Server • Single administrative interface • Set policies, manage user accounts • Maintainable S/W • Shared code base reduces replication, increases maintainability • Different protocols for different purposes • Grid FTP for wide-area transfers • Chirp for local-area accesses and reservations • Single point of control - Storage quotas/guarantees can be supported - Bandwidth can be controlled & QoS provided

7. Concurrency architecture • Three difficult goals • Low latency • High bandwidth • Multiple simultaneous clients • No single portable solution • Multiple models provide solutions on a range of different platforms • Multi-threaded • Multi-process • Single process event-driven • Control logic dynamically selects “best” model

8. Storage Layer • Abstract storage models • Virtual storage model akin to virtual protocol layer • RAID, JBOD, etc. • Memory storage model also a possibility • Provide file system interface to remote memory • Useful for store and forward buffering systems like Kangaroo • Single interface for storage resource management • Reservations • Access control • User and group management

9. NeST, Condor and the Grid • Wide area scheduling requirements: • Buffers for wide area data movements • Staging for local replicas of distributed datasets • Guaranteed availability for informed scheduling • Flexible/dynamic management of user accounts • Example: 3 1) Reserve space at NeST 2) Initiate transfer from distributed repository 3) Schedule jobs at local cluster. 4) Jobs access data locally. 1 4 2 Distributed repository Local NeST

10. Future work • HTTP administrative interface • Define metrics by which to measure • Deployability • Manageability • Reliability • Allow reservations to have a “cost” • Provide mechanisms by which files can have arbitrary, searchable metadata