Secure Location-Independent Autonomic Storage Architectures

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Secure Location-Independent Autonomic Storage
Architectures

• GR/S44501/01
• February 2004 - January 2007
• Graham Kirby, Alan Dearle, Ron Morrison Stuart
  Norcross
• School of Computer Science, University of St
  Andrews
• graham, al, ron, stuart_at_dcs.st-and.ac.uk

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Project Aims

• Desirable features of a data storage system
• unbounded capacity
• zero latency cost
• total reliability
• location independence
• simple interface
• complete security
• complete historical archive
• Aim a storage architecture approximating above,
  focusing on
• simple interface for end user (file system)
• abstracting over
• user location
• physical devices
• provision of significant benefits with acceptable
  cost

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Potential Benefits

• Simplify user experience
• home directory ubiquitously available,
  irrespective of
• machines and disks
• physical location
• firewalls
• data highly durable
• no need for backup
• simple data sharing
• uniform global name space
• Historical views
• data never over-written

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Potential Hurdles to User Adoption

• Speed and convenience must be close enough to
  that of a local disk
• Users must be able to trust system
• not to allow inappropriate access to data by
  other users
• to be sufficiently reliable for serious
  evaluation
• Need viable exit strategy
• may require that system can reproduce effects of
  users existing backup regime
• e.g. by maintaining a local copy of all data
• Financial cost
• Critical mass of nodes and users required
• envisaged architecture relies on autonomic
  management of large numbers of nodes
• Storage overhead must be low enough
• incurred through replication of data

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User Control

• End users should deal only with very high-level
  configuration
• set broad goals regarding trade-offs (or ignore
  completely)
• task of autonomic management system to try to
  achieve these goals
• Examples of trade-offs
• speed of reads and writes
• durability
• related to number and placement of replicas
• both absolute time to converge
• consistency
• how long before updates to shared data are
  visible to others?
• resource consumption
• storage, bandwidth, computation

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Control Example
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Control and Feedback Example
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Implementation Approach

• File system interface
• SMB or NFS
• Replication of files or fragments
• erasure-resilient encoding
• Placement of data
• controlled explicitly
• Routing to data
• abstracted by peer-to-peer overlay e.g. Tapestry
• Probes gauges to monitor state of system
• publish/subscribe infrastructure e.g. Siena
• Autonomic management elements
• attempt to map user goals and probe events into
  suitable low-level actions

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Challenges

• Core distributed storage infrastructure
• appropriate replication mechanisms
• Autonomic management
• low-level policies
• probe gauge infrastructure
• high-level views for users
• synthesising views from low-level events
• heuristics for adapting low-level policies to
  achieve high-level goals
• Evaluation
• simulation, local cluster, PlanetLab
• end-user adoption

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Conclusions

• Aim to design, implement and evaluate distributed
  storage system targeted at benefits to end-user
• very simple interface
• ubiquitously available
• highly durable
• append-only historical views
• Project details
• http//www-systems.dcs.st-and.ac.uk/asa/