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From Mohammad Tariq <donta...@gmail.com>
Subject Re: persistence in Hbase
Date Thu, 10 Jan 2013 15:33:37 GMT
Hello Pranshul,

      The data which you are pushing to the HBase doesn't go its final
destination directly. When you start pushing the data, it first goes to an
in-memory log file. Once the log files are considerably big, they are
merged together and put in an in-memory store called as memstore. once the
memstore crosses a certain threshold, data is finall written onto the disks
in form of HFiles.

So, whatever data has been successfully flushed to the disk will be safe,
but the you will loose the in-memory data.

You might ask why do we need two places, that too in-memory, before finally
writing the data onto the disk. This is just for the durability.


Warm Regards,

On Thu, Jan 10, 2013 at 8:48 PM, Panshul Gupta <panshul007@gmail.com> wrote:

> Hello,
> I was wondering if it is possible that I have data stored in Hbase tables
> on my 10 node cluster. I switch off (power down) my cluster. When I power
> up my cluster again, and run the HDFS and hadoop daemons, will the Hbase
> have my old data persisted in the form I left it?? or will I have to re
> import all the data??
> Thankyou for the help.
> --
> Regards,
> Panshul.
> http://about.me/panshulgupta

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