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}@dcs.st-and.ac.uk
Project Aims
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Desirable features of a data storage system
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unbounded capacity
zero latency & cost
total reliability
location independence
simple interface
complete security
complete historical archive
Aim: a storage architecture approximating above, focusing on:
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simple interface for end user (file system)
abstracting over:
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user location
physical devices
provision of significant benefits with acceptable cost
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Potential Benefits
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Simplify user experience
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‘home directory’ ubiquitously available, irrespective of:
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data highly durable
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no need for backup
simple data sharing
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machines and disks
physical location
firewalls
uniform global name space
Historical views
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data never over-written
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Potential Hurdles to User Adoption
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Speed and convenience must be close enough to that of
a local disk
Users must be able to trust system
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not to allow inappropriate access to data by other users
to be sufficiently reliable for serious evaluation
Need viable exit strategy
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may require that system can reproduce effects of user’s existing
backup regime
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Financial cost
Critical mass of nodes and users required
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e.g. by maintaining a local copy of all data
envisaged architecture relies on autonomic management of large
numbers of nodes
Storage overhead must be low enough
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incurred through replication of data
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User Control
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End users should deal only with very high-level
configuration
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set broad goals regarding trade-offs (or ignore completely)
task of autonomic management system to try to achieve these
goals
Examples of trade-offs
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speed of reads and writes
durability
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consistency
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related to number and placement of replicas
both absolute & time to converge
how long before updates to shared data are visible to others?
resource consumption
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storage, bandwidth, computation
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Control Example
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Control and Feedback Example
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Implementation Approach
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File system interface
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Replication of files or fragments
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abstracted by peer-to-peer overlay e.g. Tapestry
Probes & gauges to monitor state of system
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controlled explicitly
Routing to data
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erasure-resilient encoding
Placement of data
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SMB or NFS
publish/subscribe infrastructure e.g. Siena
Autonomic management elements
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attempt to map user goals and probe events into suitable lowlevel actions
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Challenges
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Core distributed storage infrastructure
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appropriate replication mechanisms
Autonomic management
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low-level policies
probe & gauge infrastructure
high-level views for users
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synthesising views from low-level events
heuristics for adapting low-level policies to achieve high-level
goals
Evaluation
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simulation, local cluster, PlanetLab
end-user adoption
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Conclusions
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Aim to design, implement and evaluate distributed
storage system targeted at benefits to end-user
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very simple interface
ubiquitously available
highly durable
append-only: historical views
Project details
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http://www-systems.dcs.st-and.ac.uk/asa/
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