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From John Vines <vi...@apache.org>
Subject Re: What happens when tablet is 'lost'?
Date Thu, 09 Aug 2012 13:07:14 GMT
Responding inline

John

Sent from my phone, so pardon the typos and brevity.
On Aug 9, 2012 9:02 AM, "Hugh Xedni" <hughxedni@gmail.com> wrote:
>
> Keith,
>
> From your response...
>
> "A tablets persistent data is composed of a set of files in HDFS and a
set of write ahead logs."
> "As long as the other tablet server can read the write ahead logs and
HDFS files, no data is lost."
>
> Question.
> I understand when a write arrives at a TabletServer it is written to a
Write-Ahead Log and then stored in the MemTable until flusing to HDFS via
minor compaction.
> 1) Are write ahead logs even used when data is bulk inserted into hdfs
then handed to Accumulo?

Only for the metadata entries regarding that table and those files.

> 2) If not, how is data replication achieved when using bulk insert
methods?

Hdfs replicates the data, so when the files are created in hdfs they are
replicated.
>
> --
> Thank you,
>
> Hugh Xedni
>
>
>
> On Thu, Jul 26, 2012 at 12:31 PM, David Medinets <david.medinets@gmail.com>
wrote:
>>
>> Thanks, Keith. That explanation is just what I wanted.
>
>
>
>
>

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