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From Ronen Itkin <ro...@taykey.com>
Subject Question regarding hdfs synchronously / asynchronously block replication
Date Wed, 05 Oct 2011 07:53:42 GMT
Hi all!

My question is regarding hdfs block replication.
>From the perspective of client, does the application receives an ACK for a
certain packet after it was written on the first
hadoop data node in the pipeline? or after the packet is *replicated* to all
assigned *replication* nodes?

More generaly, does Hadoop's HDFS block replication works synchronously or

synchronously --> more replications =  decrease in write performances
(client has to wait until every packet will be written to all replication
nodes before he receives an ACK).
asynchronously --> more replication has no influence on write performance
(client recieves an ACK packet after the first write to the first datadone
finishes, hdfs will complete its replication on his free time).

synchronously / asynchronously block replication - is it something
configurable ? If it is, than how can I do it?


Ronen Itkin*
Taykey | www.taykey.com

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