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From david marion <dlmar...@hotmail.com>
Subject RE: missing data blocks after active name node crashes
Date Tue, 10 Feb 2015 22:54:41 GMT
I believe therr was an issue fixed in 2.5 or 2.6 where the standby NN would not process block
reports from the DNs when it was dealing with the checkpoint process. The missing blocks will
get reported eventually.

<div>-------- Original message --------</div><div>From: Chen Song <chen.song.82@gmail.com>
</div><div>Date:02/10/2015  2:44 PM  (GMT-05:00) </div><div>To: user@hadoop.apache.org,
Ravi Prakash <ravihoo@ymail.com> </div><div>Cc:  </div><div>Subject:
Re: missing data blocks after active name node crashes </div><div>
Thanks for the reply, Ravi.

In my case, what I see constantly is there are always missing blocks every
time active name node crashes. The active name node crashes because of
timeout on journal nodes.

Could this be a specific case which could lead to missing blocks?


On Tue, Feb 10, 2015 at 2:20 PM, Ravi Prakash <ravihoo@ymail.com> wrote:

> Hi Chen!
> From my understanding, every operation on the Namenode is logged (and
> flushed) to disk / QJM / shared storage. This includes the addBlock
> operation. So when a client requests to write a new block, the metadata is
> logged by the active NN, so even if it crashes later on, the new active NN
> would still see the creation of the block.
> Ravi
>   On Tuesday, February 10, 2015 9:38 AM, Chen Song <chen.song.82@gmail.com>
> wrote:
> When the active name node crashes, it seems there is always a chance that
> the data blocks in flight will be missing.
> My understanding is that when the active name node crashes, the metadata
> of data blocks in transition which exist in active name node memory is not
> successfully captured by journal nodes and thus not available on standby
> name node when it is promoted to active by zkfc.
> Is my understanding correct? Any way to mitigate this problem or race
> condition?
> --
> Chen Song

Chen Song

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