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From Eugeny Morozov <emoro...@griddynamics.com>
Subject Re: Distribution of regions to servers
Date Wed, 26 Sep 2012 21:19:03 GMT

I have additional questions.
What is the access pattern of your queries? I mean that f.e. PrefixFilters
have to be applied for all KeyValue pairs in HFiles, which could be slow.
Or f.e. scanner setCaching option is able to decrease number of network
hops to get data from RegionServer.

Additionally, coprocessors are able to use InternalScanner instead of
ResultScanner, which is also could help greatly.

Also, the more dimension you specify, the more precise your query is, the
less data is about to be processed - family, columns, timeranges, etc.

On Wed, Sep 26, 2012 at 7:39 PM, Dan Han <dannahan2008@gmail.com> wrote:

>   Thanks for your swift response, Ramkrishna and Anoop. And I will
> explicate what we are doing now below.
>    We are trying to explore a systematic way to design the appropriate data
> schema for various applications in HBase. So we first designed several data
> schemas for each dataset and evaluate them with the same queries.  The
> queries are designed based on the requirements, such as selecting the data
> with a matching expression, finding the difference between two
> snapshots. The queries were processed with user-level Coprocessor.
>    In our experiments, we found that under some data schemas, the queries
> cannot get any results because of the connection timeout and RS crash
> sometimes. We observed that in this case, the queried data were centered in
> a few regions locating in a few region servers. We think the failure might
> be caused by the excess workload in these few region servers and the
> inappropriate load balance. To our best knowledge, this case can be avoided
> and improved by the well-distributed regions across the region servers.
>   Therefore, we have been thinking to add a monitoring and management
> component between the client and server, which can schedule the
> queries/jobs from client side and distribute the regions dynamically
> according to the current workload of each region server, the incoming
> queries and data locality.
>   Does it make sense? Just my two cents. Any comments?
> Best Wishes
> Dan Han
> On Tue, Sep 25, 2012 at 10:44 PM, Anoop Sam John <anoopsj@huawei.com>
> wrote:
> > Hi
> > Can u share more details pls? What work you are doing within the CPs
> >
> > -Anoop-
> > ________________________________________
> > From: Dan Han [dannahan2008@gmail.com]
> > Sent: Wednesday, September 26, 2012 5:55 AM
> > To: user@hbase.apache.org
> > Subject: Distribution of regions to servers
> >
> > Hi all,
> >
> >    I am doing some experiments on HBase with Coprocessor. I found that
> the
> > performance
> > of Coprocessor is impacted much by the distribution of the regions. I am
> > kind of interested in
> > going deep into this problem and see if I can do something.
> >
> >   I only searched out the discussion in the following link.
> >
> >
> http://search-hadoop.com/m/Vjhgj1lqw7Y1/hbase+distribution+region&subj=distribution+of+regions+to+servers
> >
> > I am wondering if there is any further discussion or any on-going work?
> Can
> > someone point it to me if there is?
> > Thanks in advance.
> >
> > Best Wishes
> > Dan Han
> >

Evgeny Morozov
Developer Grid Dynamics
Skype: morozov.evgeny

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