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From Andrew Wang <andrew.w...@cloudera.com>
Subject Re: HDFS Snapshots
Date Tue, 21 Oct 2014 14:53:32 GMT
Hi Pushparaj,

Based on those steps, isn't the expectation that you end up with a 0.6*size
block at the end? Blocks are append only (i.e. only grow in length), so
deleting a snapshot cannot result in a block shrinking.

Best,
Andrew

On Tue, Oct 21, 2014 at 7:20 AM, Pushparaj Motamari <pushparajxa@gmail.com>
wrote:

> Hi,
>
> Consider the scenario below.
>
> /A/file.txt  in HDFS
>
> 1. file.txt size = 0.5*(Size of Block).
>
> 2. Take Snapshot on directory A
>
> 3. Append to the file.txt, making its size as 0.6*(Size of Block)
>
> 4. Remove/delete the snapshot on folder taken in step2.
>
> My Question
> --------------------------------
> 1. How does HDFS handle when it has to decrease the size of block, as above
> when we delete the snapshot the block size has to be reduces to its
> previous size. This code is handled at datanode or Namnode?
>
> Thank You
>

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