Post on 21-Dec-2015
OceanStore/TapestryToward Global-Scale, Self-Repairing,
Secure and Persistent Storage
Anthony D. JosephJohn Kubiatowicz
Sahara Retreat, January 2003
OceanStore:2Sahara Retreat, January 2003 ©2003 UC Berkeley
OceanStore Context: Ubiquitous Computing
• Computing everywhere:– Desktop, Laptop, Palmtop– Cars, Cellphones– Shoes? Clothing? Walls?
• Connectivity everywhere:– Rapid growth of bandwidth in the interior of the net– Broadband to the home and office– Wireless technologies such as CMDA, Satelite, laser
• Where is persistent data????
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Utility-based Infrastructure
Pac Bell
Sprint
IBMAT&T
CanadianOceanStore
IBM
• Data service provided by storage federation• Cross-administrative domain • Pay for Service
OceanStore:4Sahara Retreat, January 2003 ©2003 UC Berkeley
OceanStore Data Model• Versioned Objects
– Every update generates a new version– Can always go back in time (Time Travel)
• Each Version is Read-Only– Can have permanent name– Much easier to repair
• An Object is a signed mapping between permanent name and latest version– Write access control/integrity involves managing
these mappings
Comet Analogy updates
versions
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The Path of an OceanStore Update
Second-TierCaches
Multicasttrees
Inner-RingServers
Clients
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Enabling Technology: DOLR(Decentralized Object Location and
Routing)
GUID1
DOLR
GUID1GUID2
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4
2
3
3
3
2
2
1
2
4
1
2
3
3
1
34
1
1
4 3
2
4
NodeID0xEF34
NodeID0xEF31NodeID
0xEFBA
NodeID0x0921
NodeID0xE932
NodeID0xEF37
NodeID0xE324
NodeID0xEF97
NodeID0xEF32
NodeID0xFF37
NodeID0xE555
NodeID0xE530
NodeID0xEF44
NodeID0x0999
NodeID0x099F
NodeID0xE399
NodeID0xEF40
NodeID0xEF34
Basic Tapestry MeshIncremental Prefix-based Routing
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Use of Tapestry MeshRandomization and
Locality
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Stability under Faults• Instability is the common case….!
– Small half-life for P2P apps (1 hour????)– Congestion, flash crowds, misconfiguration,
faults
• Must Use DOLR under instability!– The right thing must just happen
• Tapestry is natural framework to exploit redundant elements and connections– Multiple Roots, Links, etc.– Easy to reconstruct routing and location
information– Stable, repairable layer
• Thermodynamic analogies: – Heat Capacity of DOLR network– Entropy of Links (decay of underlying order)
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Single Node Tapestry
Transport Protocols
Network Link Management
Application Interface / Upcall API
OceanStoreApplication-LevelMulticast
OtherApplications
RouterRouting Table
&Object Pointer DB
Dynamic Node
Management
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It’s Alive! • Planet Lab global network
– 98 machines at 42 institutions, in North America, Europe, Australia (~ 60 machines utilized)
– 1.26Ghz PIII (1GB RAM), 1.8Ghz PIV (2GB RAM)– North American machines (2/3) on Internet2
• Tapestry Java deployment– 6-7 nodes on each physical machine– IBM Java JDK 1.30– Node virtualization inside JVM and SEDA– Scheduling between virtual nodes increases
latency
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Segments of OceanStorewithin Sahara Retreat
• Today (5:30pm – 6:00pm)– OceanStore Long-Term Archival Storage
• Tomorrow morning session (8:30am-10:00am)– Tapestry status and deployment information
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For more info:http://oceanstore.org
• OceanStore vision paper for ASPLOS 2000“OceanStore: An Architecture for Global-Scale
Persistent Storage”
• OceanStore Prototype (FAST 2003):“Pond: the OceanStore Prototype”
• Tapestry algorithms paper (SPAA 2002):“Distributed Object Location in a Dynamic Network”
• Upcoming Tapestry Deployment Paper (JSAC)“Tapestry: a Global-Scale Overlay for Rapid Service Deployment”
• Probabilistic Routing (INFOCOM 2002):“Probabilistic Location and Routing”
• Upcoming CACM paper (not until February):– “Extracting Guarantees from Chaos”