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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}@dcs.st-and.ac.uk
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:
data highly durable
no need for backup
simple data sharing
machines and disks
physical location
firewalls
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 user’s existing
backup regime
Financial cost
Critical mass of nodes and users required
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
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
consistency
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
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
Replication of files or fragments
abstracted by peer-to-peer overlay e.g. Tapestry
Probes & gauges to monitor state of system
controlled explicitly
Routing to data
erasure-resilient encoding
Placement of data
SMB or NFS
publish/subscribe infrastructure e.g. Siena
Autonomic management elements
attempt to map user goals and probe events into suitable lowlevel 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/
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