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Storage management and caching in PAST, a large-scale, persistent peer-to-peer storage utility

Storage management and caching in PAST, a large-scale, persistent peer-to-peer storage utility. Antony Rowstron, Peter Druschel. Introduction. PAST is an Internet-based, peer-to-peer global storage utility. It aims to provide strong persistence, high availability, scalability and security.

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Storage management and caching in PAST, a large-scale, persistent peer-to-peer storage utility

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  1. Storage management and caching in PAST, a large-scale, persistent peer-to-peer storage utility Antony Rowstron, Peter Druschel

  2. Introduction • PAST is an Internet-based, peer-to-peer global storage utility. • It aims to provide strong persistence, high availability, scalability and security. • PAST employs Pastry as the routing scheme. • Pastry is an efficient routing scheme used to reliably route client requests to the appropriate nodes.

  3. PAST Operations • fileId=Insert(name, owner-credentials, k, file) fileId is 160-bit, while nodeId is 128-bit; fileId nodeId • file=Lookup(fileId) Reliably retrieve a copy of the file • Reclaim(fileId, owner-credentials) Notice: Reclaim doesn’t guarantee that the file is no longer available after it was reclaimed. 128 Bits 32 Bits M L 128 Bits

  4. Storage Management • Design Goals: • Allow high global storage utilization • Gracefully degrade as the system approaches the maximal utilization • Load balancing: • Replica diversion • File diversion

  5. Replica Diversion • Replica diversion is to accommodate differences in the storage capacity and utilization of nodes within a leaf set. File is stored in B due to the less capacity in A B C C is the k+1th closest node, which stores the pointer in case of the failure of node A An entry points to B A A is the right node to store the file, but has insufficient space

  6. File Diversion • The k closest nodes to the fileId could not accommodate the file nor divert the replicas; then, a file diversion is invoked. • The client generates a new fileId, and retries to insert the file. • Repeat the second step up to 3 times. • If it still fails, an error is reported to the application.

  7. Caching • PAST nodes use the “unused” portion of their advertised disk space to cache files. • Caching in PAST is based on GreedyDual-Size (GD-S) policy, which was originally developed for caching Web proxies.

  8. Experimental Results *This graph is from the paper.

  9. Question?

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