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From Keith Turner <>
Subject Re: What happens when tablet is 'lost'?
Date Thu, 26 Jul 2012 15:05:37 GMT
A tablets persistent data is composed of a set of files in HDFS and a
set of write ahead logs.  The !METADATA table stores the names of the
HDFS files and write ahead logs.  When a tablet server goes down, the
master ask another tablet server to load the tablet.  As long as the
other tablet server can read the write ahead logs and HDFS files, no
data is lost.   If enough servers go down such that HDFS files or
write ahead logs lose access to data, then the tablet will not be
accessible until the data node and/or loggers come back online.

On Thu, Jul 26, 2012 at 7:54 AM, David Medinets
<> wrote:
> This question was asked at a presentation gave yesterday and I
> realized that I don't know the answer. A tablet serves a specific key
> of keys which is disjoint from all other tablets. Say a table has ten
> tablets with perfectly distributed keys so each tablet serves 10% of
> the data. If tablet A is lost, does the system lose access to the
> first 10% of the data?

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