View source for DistOS 2014W Lecture 20


== Cassandra ==

Cassandra is essentially running a BigTable interface on top of a Dynamo infrastructure.  BigTable uses GFS' built-in replication and Chubby for locking.  Cassandra uses gossip algorithms: [http://dl.acm.org/citation.cfm?id=1529983 Scuttlebutt].  Apache Zookeeper is used for distributed configuration.

== Comet ==

The major idea behind Comet is triggers/callbacks.  There is an extensive literature in extensible operating systems, basically adding code to the operating system to better suit my application.

[https://www.usenix.org/conference/osdi10/comet-active-distributed-key-value-store The presentation video of Comet]

Cassandra
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Cassandra is essentially running a BigTable interface on top of a Dynamo infrastructure.  BigTable uses GFS' built-in replication and Chubby for locking.  Cassandra uses gossip algorithms: [http://dl.acm.org/citation.cfm?id=1529983 Scuttlebutt].  Apache Zookeeper is used for distributed configuration.
 		 	
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Google developed its technology interbally and used for competitive advantage.
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== Comet ==
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Facebook developed its technology in open source manner.
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Gpl 3 you have to provide code with binary
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[https://www.usenix.org/conference/osdi10/comet-active-distributed-key-value-store The presentation video of Comet]
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In AGPL addtional service also be given with source code.
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Bigtable needs gfs.cassandra depends on server's file system.Anil feels cassndra cluster is easy to setup.
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Bigtable is designed for batch updates.cassandra is for hqbdling realtime stuff.
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Schema design is explained in inbox example.it does does not give clarity about how table will look like.Anil thinks they store lot data with messages which makes table crappy.
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Cassandra is design for high speed access and online operation.
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Zookeeper is similar to chhuby
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Zookeeper is for node level information
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Gossip is more about key partitioning
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Zookeeper is for configuration of new node.
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It writes in immutable way like functional programming.there is no assignment in functional programming.