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From Minh Duc Nguyen <mdngu...@gmail.com>
Subject Re: In memory table after using 'alter'
Date Wed, 27 Jun 2012 16:00:50 GMT
Sever, the IN_MEMORY option doesn't change when table content is
transferred into RAM.  Whether set to true or false, the blocks of
data are only loaded into memory after a normal retrieval operation.
When IN_MEMORY is set to true, HBase just tries to keep data in memory
more aggressively than it normally would.  This wiki explains it in
more detail:

http://jimbojw.com/wiki/index.php?title=Understanding_HBase_column-family_performance_options

   ~ Minh

On Wed, Jun 27, 2012 at 7:18 AM, Sever Fundatureanu
<fundatureanu.sever@gmail.com> wrote:
> Hello,
>
> I initially created a table without the IN_MEMORY option enabled and loaded
> some data into it. Then I disabled it, modified the IN_MEMORY option using
> the hbase shell 'alter' command, re-enabled it and finally ran a major
> compaction. I do notice now the memory usage of the region servers has
> increased. However for some queries I am still getting faster responses
> only the 2nd time, as if I'm hitting the cache. Can someone tell me when
> does the table content get transferred into RAM if IN_MEMORY option is
> enabled like above?
>
> Thank you,
> --
> Sever Fundatureanu
>
> Vrije Universiteit Amsterdam
> E-mail: fundatureanu.sever@gmail.com

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