DistOS 2014W Lecture 20 - Revision history

36chambers: /* Back to Cassandra */

2014-04-24T16:15:50Z

Back to Cassandra

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	Cassandra writes in an immutable way like functional programming. There is no assignment in functional programming. It tries to eliminate side effects. Data is just binded you associate a name with a value.		Cassandra writes in an immutable way like functional programming. There is no assignment in functional programming. It tries to eliminate side effects. Data is just binded you associate a name with a value.

			Mutation is difficult to parallel due to the coordination of the current state.
			To escape abstraction: create code, give/add it to the operating system, and change the semantics of the operating system to better suit the application.
			In general, extensible systems are bad.

	Cassandra -		Cassandra -

36chambers: /* Comet */

2014-04-24T15:46:35Z

Comet

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	* Uses Lua		* Uses Lua
	* Provided extensibility in an untrusted environment. Dynamo, by contrast, was extensible but only in a trusted environment.		* Provided extensibility in an untrusted environment. Dynamo, by contrast, was extensible but only in a trusted environment.
	* Why do we care? We don't really. Why would you want this extensibility? You wouldn't. It isn't worth the cost. Current systems currently have an allowance for tuneability.		* Why do we care? We don't really. Why would you want this extensibility? You wouldn't. It isn't worth the cost. Current systems currently have an allowance for tuneability. This extensibility only has use under undesirable circumstances.


	== Other ==		== Other ==

36chambers: /* A brief look at Open Source */

2014-04-24T15:45:10Z

A brief look at Open Source

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	*GFS optimized for data-analyst cluster.		*GFS optimized for data-analyst cluster.

	While discussing Hbase versus Cassandra discussed why two projects with same notion are supported? Apache as a community. For any tool in computer science, particularly software tools, its important to have more than one good implementation. Only time it doesn't happen is because of market interference. An example of this was Microsoft Word, which took out most of the competition.		While discussing Hbase versus Cassandra discussed why two projects with same notion are supported? Apache as a community. For any tool in computer science, particularly software tools, its important to have more than one good implementation. Only time it doesn't happen is because of market interference. An example of this was Microsoft Word, which took out most of the competition. Different implementations are commonly due to programmers disagreeing on concepts and designs.

36chambers: /* A brief look at Open Source */

2014-04-24T15:43:04Z

A brief look at Open Source

← Older revision		Revision as of 15:43, 24 April 2014
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	*GFS optimized for data-analyst cluster.		*GFS optimized for data-analyst cluster.

	While discussing Hbase versus Cassandra discussed why two projects with same notion are supported? Apache as a community. For any tool in CS, particularly software tools, its ~~actually~~ important to have more than one good implementation. Only time it doesn't happen because of market ~~realities~~.		While discussing Hbase versus Cassandra discussed why two projects with same notion are supported? Apache as a community. For any tool in computer science, particularly software tools, its important to have more than one good implementation. Only time it doesn't happen is because of market interference. An example of this was Microsoft Word, which took out most of the competition.


	Hadoop is a set of technologies that represent the open source equivalent of		Hadoop is a set of technologies that represent the open source equivalent of

36chambers at 15:40, 24 April 2014

2014-04-24T15:40:18Z

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	*Facebook managed to be very good with contributing to open source projects that they were a part of, and stay alive in the open source projects that they start. Google works internally and pitches their code "over the fence."		*Facebook managed to be very good with contributing to open source projects that they were a part of, and stay alive in the open source projects that they start. Google works internally and pitches their code "over the fence."
	* He talked little bit about licences. With GPL3 you have to provide code with binary. In AGPL additional service also be given with source code.		* He talked little bit about licences. With GPL3 you have to provide code with binary. In AGPL additional service also be given with source code.
	*GFS optimized for data-analyst cluster		*GFS optimized for data-analyst cluster.

	While discussing Hbase versus Cassandra discussed why two projects with same notion are supported? Apache as a community. For any tool in CS, particularly software tools, its actually important to have more than one good implementation. Only time it doesn't happen because of market realities.		While discussing Hbase versus Cassandra discussed why two projects with same notion are supported? Apache as a community. For any tool in CS, particularly software tools, its actually important to have more than one good implementation. Only time it doesn't happen because of market realities.
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	* Lighter weight		* Lighter weight
	* All most of the readings are part of Apache		* All most of the readings are part of Apache
	* More designed for online updates for ~~interactive lower latency~~		* More designed for low latency online updates and more optimized for reads.
	* Once they write to disk they only read back		* Once they write to disk they only read back
	* Scalable multi master database with no single point of failure		* Scalable multi master database with no single point of failure

36chambers: /* A brief look at Open Source */

2014-04-24T15:36:48Z

A brief look at Open Source

← Older revision		Revision as of 15:36, 24 April 2014
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	*Facebook managed to be very good with contributing to open source projects that they were a part of, and stay alive in the open source projects that they start. Google works internally and pitches their code "over the fence."		*Facebook managed to be very good with contributing to open source projects that they were a part of, and stay alive in the open source projects that they start. Google works internally and pitches their code "over the fence."
	* He talked little bit about licences. With GPL3 you have to provide code with binary. In AGPL additional service also be given with source code.		* He talked little bit about licences. With GPL3 you have to provide code with binary. In AGPL additional service also be given with source code.
			*GFS optimized for data-analyst cluster

	While discussing Hbase versus Cassandra discussed why two projects with same notion are supported? Apache as a community. For any tool in CS, particularly software tools, its actually important to have more than one good implementation. Only time it doesn't happen because of market realities.		While discussing Hbase versus Cassandra discussed why two projects with same notion are supported? Apache as a community. For any tool in CS, particularly software tools, its actually important to have more than one good implementation. Only time it doesn't happen because of market realities.

36chambers: /* A brief look at Open Source */

2014-04-24T15:26:25Z

A brief look at Open Source

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	=== A brief look at Open Source ===		=== A brief look at Open Source ===

	Initialy Anil talked about ~~google~~ versus ~~facebook~~ approach to technologies.		Initialy Anil talked about Google versus Facebook approach to technologies.
	* Google has been good at publishing papers on their distributed system structure.		* Google has been good at publishing papers on their distributed system structure.
	* Google developed its technology internally and used for competitive advantage.		* Google developed its technology internally and used it for competitive advantage.
	* Facebook developed its technology in open source manner. They needed to create an open source community to keep up.		* People try to implement Google’s methods in the open source arena.
			* Google had proprietary technology but Facebook wanted open design.
			* Facebook developed its technology in open source manner. They needed to create an open source community to keep up.
			*Facebook managed to be very good with contributing to open source projects that they were a part of, and stay alive in the open source projects that they start. Google works internally and pitches their code "over the fence."
	* He talked little bit about licences. With GPL3 you have to provide code with binary. In AGPL additional service also be given with source code.		* He talked little bit about licences. With GPL3 you have to provide code with binary. In AGPL additional service also be given with source code.

36chambers: /* A brief look at Open Source */

2014-04-24T15:18:45Z

A brief look at Open Source

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	=== A brief look at Open Source ===		=== A brief look at Open Source ===

	Initialy Anil talked about google versus facebook approach to technologies.		Initialy Anil talked about google versus facebook approach to technologies.
			* Google has been good at publishing papers on their distributed system structure.
	* Google developed its technology internally and used for competitive advantage.		* Google developed its technology internally and used for competitive advantage.
	* Facebook developed its technology in open source manner. They needed to create an open source community to keep up.		* Facebook developed its technology in open source manner. They needed to create an open source community to keep up.

36chambers: /* Back to Cassandra */

2014-04-21T09:49:48Z

Back to Cassandra

← Older revision		Revision as of 09:49, 21 April 2014
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	* Not just a key value store. It is a multi dimensional map. You can look up different columns, etc. The data is more structured than a Key-Value store.		* Not just a key value store. It is a multi dimensional map. You can look up different columns, etc. The data is more structured than a Key-Value store.
	* In a key value store, you can only look up the key. Cassandra is much richer than this.		* In a key value store, you can only look up the key. Cassandra is much richer than this.
			* A fundamental difference in Cassandra is that adding columns is trivial.

	Bigtable vs. Cassandra:		Bigtable vs. Cassandra:

Cdelahou: Added a few other points for Comet.

2014-04-20T02:04:52Z

Added a few other points for Comet.

← Older revision		Revision as of 02:04, 20 April 2014
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	== Comet ==		== 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. "Generally, extensible systems suck." -[[User:Soma]]		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. "Generally, extensible systems suck." -[[User:Soma]] This was popular before operating systems were open source.

	[https://www.usenix.org/conference/osdi10/comet-active-distributed-key-value-store The presentation video of Comet]		[https://www.usenix.org/conference/osdi10/comet-active-distributed-key-value-store The presentation video of Comet]
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	Researchers try to provide the ability to extend a DHT without requiring a substantial investment of effort to modify its implementation.They try to implement to isolation and safety using restricting system access,restricting resource consumption and restricting within-Comet communication.		Researchers try to provide the ability to extend a DHT without requiring a substantial investment of effort to modify its implementation.They try to implement to isolation and safety using restricting system access,restricting resource consumption and restricting within-Comet communication.

			* Provids callbacks (aka. Database triggers)
			* Provides DHT platform that is extensible at the application level
			* Uses Lua
			* Provided extensibility in an untrusted environment. Dynamo, by contrast, was extensible but only in a trusted environment.
			* Why do we care? We don't really. Why would you want this extensibility? You wouldn't. It isn't worth the cost. Current systems currently have an allowance for tuneability.


			== Other ==

	* if someone wants to understand the consistent hashing in detail, here is a blog which explains it really well, this blog has other great posts in the field of distributed system as well -		* if someone wants to understand the consistent hashing in detail, here is a blog which explains it really well, this blog has other great posts in the field of distributed system as well -
	http://loveforprogramming.quora.com/Distributed-Systems-Part-1-A-peek-into-consistent-hashing *		http://loveforprogramming.quora.com/Distributed-Systems-Part-1-A-peek-into-consistent-hashing *