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HBase >> mail # user >> Hbase scans taking a lot of time


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Re: Hbase scans taking a lot of time
This is what I think, Sorry for my ignorance.

I want to use the property of Hbase( i.e columnar DB) so that only the
required columns are accessed. For this I kept a large number of column
families.

But I am still not understanding....what is happening as there is no disk
I/O only High CPU and some network activity.
Why is the scan taking more time than the time to populate the Hbase.

-Vibhav
On Fri, Jan 25, 2013 at 11:36 PM, Jean-Marc Spaggiari <
[EMAIL PROTECTED]> wrote:

> Hi Vibhav,
>
> Do you really need 13 diffefent columns familly? Can't you find a way
> to bundle that into 1 or 2 max CF? Maybe by prefixing the colument
> name?
>
> That might help...
>
> JM
>
> 2013/1/25, Vibhav Mundra <[EMAIL PROTECTED]>:
> > The number of column families I have is 13, which I guess is okie?
> >
> > -Vibhav
> >
> >
> > On Fri, Jan 25, 2013 at 11:01 PM, Luke Lu <[EMAIL PROTECTED]> wrote:
> >
> >> You'll have this problem if you have a large number of column families
> >> being scanned/populated at the same time. Make sure the data you
> >> scan/populate frequently are in the same column family (you can have
> many
> >> columns in a column family). Unlike BigTable/Hypertable which has the
> >> concept of locality/access groups, HBase always stores column families
> in
> >> separate files, essentially making column family not only a logic
> >> grouping
> >> mechanism but also a physical locality group.
> >>
> >>
> >> On Fri, Jan 25, 2013 at 1:10 AM, Vibhav Mundra <[EMAIL PROTECTED]>
> wrote:
> >>
> >> > I am facing a very strange problem with HBase.
> >> >
> >> > This what I did:
> >> > a) Create a table, using pre partioned splits.
> >> > b) Also the column familes are zipped with lzo compression.
> >> > c) Using the above configuration I am able to populate 2 million row
> >> > per
> >> > min in the Hbase.
> >> > d) I have created a table with 300 million odd rows, which roughy took
> >> me 3
> >> > hours to populate and the data size is of 25GB.
> >> >
> >> > e) But when I query for data the performance I am getting is very bad.
> >> >    Basically this is what I am seeing: High CPU, no disk I/O and
> >> > network
> >> > I/O is happening at the rate of 6~7MB secs.
> >> >
> >> >
> >> > Because of this, if I scan the entries of the table using Hive it is
> >> taking
> >> > ages.
> >> > Basically it is taking around 24 hours to scan the table. Any idea, of
> >> how
> >> > to debug.
> >> >
> >> >
> >> > -Vibhav
> >> >
> >>
> >
>