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Policies in Distributed Data Storage

Policies in Distributed Data Storage. Presented by: Ajay Potnis Professor: Craig E. Wills December 2000. Acknowledgements. Professor Craig E. Wills Uresh Vahalia Xiaoye Jiang Gary Ma Jiannan Zheng Yael Melman Mrunal Potnis Aditya Potnis. Goal. Study various distributed architectures

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Policies in Distributed Data Storage

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  1. Policies in Distributed Data Storage Presented by: Ajay Potnis Professor: Craig E. Wills December 2000

  2. Acknowledgements • Professor Craig E. Wills • Uresh Vahalia • Xiaoye Jiang • Gary Ma • Jiannan Zheng • Yael Melman • Mrunal Potnis • Aditya Potnis

  3. Goal • Study various distributed architectures • NFS • xFS • SAN • SSFS • Conclusion

  4. Direct Attached Storage Data Storage Unit Data on SCCI/Fibre

  5. Direct Attached Storage • Channel I/O Speed • Can select the desired storage • No sharing • No flexibility

  6. NFS Data Storage Unit Data and Metadata Data on SCCI/Fibre File Server

  7. NFS • Simple client server semantics using LAN/WAN • Server is the owner of file system • Uses RPC for communication • NFS with Mount protocol makes FS locally available • Support for advisory locking using NLM • Caching in memory/on disk improves performance on clients (stale data) • Data can be shared by multiple clients • Administration is easy due to centralization of data • Server can provide scalability, high availability, online maintenance, etc.

  8. xFS Client Client and Manager Forward Request Data Storage Unit Data Request Forward Request Data on SCCI/Fibre Data Storage Server

  9. xFS • Server-less architecture (clients, storage servers and managers) • Distributes cache, storage and metadata management over machines • Uses a stateful protocol • Uses Active Messages instead of RPC for communication • Multiple managers could lead to more network traffic • Flexibility adding many clients, managers and storage servers • Client write data to storage server before giving it to another client to avoid consistency problems in failures • Increased circular dependencies and complexities

  10. SAN (switched fabric) File Server Data Storage Unit Switch Data Data Data on Fibre

  11. SAN • Connects multiple clients to multiple storage drives • Storage can be configured at will • Needs good management tools and good Sys Admin skills • No seamless sharing of same storage by multiple clients/servers

  12. SSFS Client 1 Data on SCCI / Fibre 1.Metadata Request 2. Metadata Data Storage Unit uses SAN Data on SCCI / Fibre for NAS Server 2. Metadata 1.Metadata Request Data on SCCI / Fibre Client 2

  13. SSFS • Client-Server-Storage semantics using NAS and SAN • NAS for sharing, SAN for channel I/O speed • File sharing among heterogeneous clients • Concurrent sharing among NAS and SAN clients • Server is the owner of metadata and storage • RPC communication for metadata exchange over network • Caching in memory improves performance on clients (stale data not possible because of callbacks) • Read/Write throughput increased since data goes at channel speed (can use multiple SCSI/fibre paths to write) • Multiple clients can use the same storage device • Scalability, high availability, transparent to applications • Failure recovery built in the protocol

  14. Conclusion • Why not get two birds in one shot?

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