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From Jonathan Gray <jg...@facebook.com>
Subject RE: Porting SQL DB into HBASE
Date Wed, 31 Mar 2010 16:53:41 GMT

HBase can handle a good number of tables, but tens or maybe a hundred.  If you have 500 tables
you should definitely be rethinking your schema design.  The issue is less about HBase being
able to handle lots of tables, and much more about whether scattering your data across lots
of tables will be performant at read time.

1)  Impossible to answer that question without knowing the schemas of the existing tables.

2)  Not really any relation between fault tolerance and the number of tables except potentially
for recovery time but this would be the same with few, very large tables.

3)  No difference in write performance.  Read performance if doing simple key lookups would
not be impacted, but most like having data spread out like this will mean you'll need joins
of some sort.

Can you tell more about your data and queries?


> -----Original Message-----
> From: kranthi reddy [mailto:kranthili2020@gmail.com]
> Sent: Wednesday, March 31, 2010 3:05 AM
> To: hbase-user@hadoop.apache.org
> Subject: Porting SQL DB into HBASE
> Hi all,
>         I have run into some trouble while trying to port SQL DB to
> Hbase.
> The problem is my SQL DB has around 500 tables (approx) and it is very
> badly
> designed. Around 45-50 tables could be denormalised into a single table
> and
> the remaining tables are static tables. My doubts are
> 1) Is it possible to port this DB (Tables) to Hbase? If possible how?
> 2) How many tables can Hbase support with tolerance towards failure?
> 3) When so many tables are inserted, how is the performance going to be
> effected? Will it remain same or degrade?
> One possible solution I think is using column family for each table.
> But as
> per my knowledge and previous experiments, I found Hbase isn't stable
> when
> column families are more than 5.
> Since every day large quantities of data is ported into the DataBase,
> stability and fail proof system is highest priority.
> Hoping for a positive response.
> Thank you,
> kranthi

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