Ivy

Ivy

Ivy is a multi-user read/write P2P file system. It has no centralized component. Users in the system are not supposed to trust either storage system or other users. Participants solely have a set of logs (one per participant) which are stored on the DHash DHT. Each user could search in any log but perform changes only on its own log. That’s why here there is no need of locking. At the same time each user makes snapshots of the latest current situation (and they are storing, in their Ivy log msgs, previous record of DHash key). System provides NFS-like semantic. But the performance is 2-3 time slower that NFS.

Most probably then details of this paper should be reviewed once more (principles of design).

Related Works:

Problems that were the main force to design this systems are read-only limitation or single-publisher data in storage systems. Sprite LFS uses a single log managed by a single server (when Ivy uses multiple logs to let multiple participant update the file system). Zebra maintain per-client log of file contents, but meta-data are serialized through a single meta-data server ( Ivy avoid using single meta-data server). xFS distributes both data and meta-data across participants and it has meta-data centralization (when Ivy avoid it but performs a bit slower and adheres less strictly to serial semantics). Frangipani - two layers: dist. storage service and set of symmetric file servers. But it uses locks to serialize updates to meta-data. Harp system consist of a small cluster. Elephant file system allows all the operation to be undone in the specific defined time. Coda, Ficus, Bayou, BFS, OceanStore, Fairsite, TDB, Speitzer - need some small review as well. (Most probably I’ll do it later).

Advantages:

  • Decentralized storage – no central point of failure

Disadvantages:

  • Security measures happen after the disaster
  • Not so scalable
  • They claim that it doesn’t require users trust

Volunteer Systems:

  • May fit more in volunteer system rather than P2P. Specifically a volunteer system with full trust between users.
decentralized_storage_systems/ivy.txt · Last modified: 2012/04/23 01:00 by julia
 
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