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Date: Mon, 5 Nov 2007 15:48:51 -0800 (PST)
From: "Sanjay Radia (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-1989) Add support for simulated Data
 Nodes  - helpful for testing and performance benchmarking of the Name Node
 without having a large cluster
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    [ https://issues.apache.org/jira/browse/HADOOP-1989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12540298 ] 

Sanjay Radia commented on HADOOP-1989:
--------------------------------------

Tried to put the simulated implementations inside the test tree; unfortunately, it required that the test tree be compiled before the main src tree.
For example startDataNode refers to the simulated impl if it is starting the simulated fsdataset. Note that we are reusing 
the datanode implementation; only the fsdataset is different.


> Add support for simulated Data Nodes  - helpful for testing and performance benchmarking of the Name Node without having a large cluster
> ----------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-1989
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1989
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>            Reporter: Sanjay Radia
>            Priority: Minor
>         Attachments: SimulatedStoragePatchSubmit.txt
>
>
> Proposal is to add an implementation for a Simulated Data Node.
> This will 
>   - allow one to test certain parts of the system (especially the Name Node, protocols) much more easily and efficiently.
>   - allow one to run performance benchmarks on the Name node without having a large cluster.
>   - Inject faults for testing (e.g. one can add random faults based probability parameters).
> The idea is that the Simulated Data Node will
>  - discard any data written to blocks (but remember the blocks and their sizes)
>  - generate fixed data on the fly when blocks are read (e.g. block is fixed set of bytes or repeated sequence of strings).
> The Simulated Data Node can also be used for fault injection.
> The data node can be parameterized with probabilities that allow one to control:
>   - Delays on reads and writes, creates, etc
>   - IO Exceptions
>  - Loss of blocks 
>  - Failures

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