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From Xine Jar <xineja...@googlemail.com>
Subject Re: number of tablets and hbase table size
Date Tue, 01 Sep 2009 17:05:12 GMT
Thank you,

 while the answers on Q3 and Q4 were clear enough I still have some problems
with the first two questions.

-which entry in the hbase-default.xml allows me to check the size of a
tablet?

-In hadoop, I used to copy a file to the DFS by doing "bin/hadoop dfs
-copyFromLocal filesource fileDFS".
 Having this file in the DFS I could list it "bin/hadoop dfs -ls" and check
its size by doing "bin/hadoop dfs -du fileDFS"
 But when I create an hbase table, this table does not appear in the DFS.
Therefore the latter command gives an error it cannot find
 the table!!  So how can I point to the folder of the table?

Regards,
CJ


On Tue, Sep 1, 2009 at 5:00 PM, Jean-Daniel Cryans <jdcryans@apache.org>wrote:

> Anwers inline.
>
> J-D
>
> On Tue, Sep 1, 2009 at 10:53 AM, Xine Jar<xinejar22@googlemail.com> wrote:
> > Hallo,
> > I have a cluster of 6 nodes running hadoop0.19.3 and hbase 0.19.1. I have
> > managed to write small programs to test the settings and everything seems
> to
> > be fine.
> >
> > I wrote a mapreduce program reading a small hbase table (100 rows, one
> > familiy colum, 6 columns) and summing some values. In my opinion the job
> is
> > slow, it
> > is taking 19sec. I would like to look closer what is going, if the table
> is
> > plit into tablets or not ...Therefore I appreciate if someone can answer
> my
> > following questions:
>
> With that size, that's expected. You would be better off scanning your
> table directly instead, MapReduce has a startup cost and 19 seconds
> isn't that much.
>
> >
> >
> > *Q1 -Does  the value of "hbase.hregion.max.filesize" in the
> > hbase-default.xml indicate the maximum size of a tablet in bytes?
>
> It's the maximum size of a family (in a region) in bytes.
>
> >
> > Q2- How can I know the size of the hbase table I have created? (I guess
> the
> > "Describe" command from the shell does not provide it)
>
> Size as in disk space? You could use the hadoop dfs -du command on
> your table's folder.
>
> >
> > Q3- Is there a way to know the real number of tablets constituting my
> table?
>
> In the Master's web UI, click on the name of your table. If you want
> to do that programmatically, you can indirectly do it by calling
> HTable.getEndKeys() and the size of that array is the number of
> regions.
>
> >
> > Q4- Is there a way to get more information on the tablets handeled by
> each
> > regionserver? (their number, the rows constituting each tablet)   *
>
> In the Master's web UI, click on the region server you want info for.
> Getting the number of rows inside a region, for the moment, can't be
> done directly (requires doing a scan between the start and end keys of
> a region and counting the number of rows you see).
>
> >
> > Thank you for you help,
> > CJ
> >
>

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