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From Erik Holstad <erikhols...@gmail.com>
Subject Re: Some HBase FAQ
Date Mon, 13 Apr 2009 16:17:04 GMT
On Mon, Apr 13, 2009 at 7:12 AM, Puri, Aseem <Aseem.Puri@honeywell.com>wrote:

> Hi
>
>            I am new HBase user. I have some doubts regards
> functionality of HBase. I am working on HBase, things are going fine but
> I am not clear how are things happening. Please help me by answering
> these questions.
>
>
>
> 1.      I am inserting data in HBase table and all regions get balanced
> across various Regionservers. But what will happens when data increases
> and there is not enough space in Regionservers to accommodate all
> regions. So I will like this that some regions in Regionserver and some
> are at HDFS but not on Regionserver or HBase Regioservers stop taking
> new data?
>
Not really sure what you mean here, but if you are asking what to do when
you are
running out of disk space on the regionservers, the answer is add another
machine
or two.


>
>
>
> 2.      When I insert data in HBase table, 3 to 4 mapfiles are generated
> for one category, but after some time all mapfiles combines as one file.
> Is this we call minor compaction actually?
>
When all current mapfiles and memcache are combined into one files, this
is called major compaction, see BigTable paper for more details.


>
>
>
> 3.      For my application where I will use HBase will have updates in a
> table frequently. Should is use some other database as a intermediate to
> store data temporarily like MySQL and then do bulk update on HBase or
> should I directly do updates on HBase. Please tell which technique will
> be more optimized in HBase?
>
HBase is fast for reads which has so far been the main focus of the
development, with
0.20 we can hopefully add even fast random reading to it to make it a more
well rounded
system. Is HBase too slow for you today when writing to it and what are your
requirements?

Regards Erik

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