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From Vijaya Narayana Reddy Bhoomi Reddy <vijay.bhoomire...@gmail.com>
Subject HDFS File Writes & Reads
Date Tue, 17 Jun 2014 11:17:43 GMT

I have a basic question regarding file writes and reads in HDFS. Is the
file write and read process a sequential activity or executed in parallel?

For example, lets assume that there is a File File1 which constitutes of
three blocks B1, B2 and B3.

1. Will the write process write B2 only after B1 is complete and B3 only
after B2 is complete or for a large file with many blocks, can this happen
in parallel? In all the hadoop documentation, I read this to be a
sequential operation. Does that mean for a file of 1TB, it takes three
times more time than a traditional file write? (due to default replication
factor of 3)
2. Is it similar in the case of read as well?

Kindly someone please provide some clarity on this...


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