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From Doug Meil <doug.m...@explorysmedical.com>
Subject Re: No. of families
Date Fri, 30 Dec 2011 17:26:23 GMT

The origin on the lower number of CF's wasn't so much on the reads but on
the writes (and GC churn) that happens with MemStore flushes per Store.




On 12/29/11 1:18 AM, "lars hofhansl" <lhofhansl@yahoo.com> wrote:

>Less is not necessarily better. HBase can ignore stores (column families)
>during a scan or get if thatno columns in that family were requested.
>
>So what you want to do is group columns that are typically queried
>together in a single column family, and put
>columns that are not typically queried together in separate families.
>
>
>-- Lars
>
>
>----- Original Message -----
>From: Rohit Kelkar <rohitkelkar@gmail.com>
>To: user@hbase.apache.org
>Cc: 
>Sent: Wednesday, December 28, 2011 9:01 PM
>Subject: Re: No. of families
>
>When we say less column families, how much is less? Is this guided by
>a ratio of the number of rows stored in the Htable to number of column
>families. Or number of tables to number of column families. If I
>understand correctly, the content of each column family is stored in a
>separate file. So does it have anything to do with the disk space
>allocated to hadoop?
>
>- Rohit Kelkar
>
>On Wed, Dec 28, 2011 at 10:14 PM, Mohammad Tariq <dontariq@gmail.com>
>wrote:
>> Hi Doug,
>>
>>  Thanks a lot for the reply.Ya, I had asked a similar
>> question.Actually I am stuck with some schema design issue.I am sorry,
>> the intention was not to ask the same thing repeatedly.I'll try to
>> figure it out with the help of guidelines provided.Many thanks.
>>
>> Regards,
>>     Mohammad Tariq
>>
>>
>>
>> On Wed, Dec 28, 2011 at 7:24 PM, Doug Meil
>> <doug.meil@explorysmedical.com> wrote:
>>>
>>> Hi there-
>>>
>>> re:  "number of CF's"
>>>
>>> Yes.  Fewer is better.
>>>
>>> http://hbase.apache.org/book.html#schema
>>>
>>> re:  "sub column families"
>>>
>>>
>>> There aren't "sub column families" - it's just columns (within a CF).
>>>
>>> http://hbase.apache.org/book.html#datamodel
>>>
>>>
>>> If I am not mistaken you asked a similar question to the dist-list a
>>>few
>>> weeks ago. The answers haven't changed.
>>>
>>>
>>>
>>>
>>>
>>>
>>> On 12/28/11 2:53 AM, "Mohammad Tariq" <dontariq@gmail.com> wrote:
>>>
>>>>Hello all,
>>>>
>>>>    Having less no. of column families is advisable. It is feasible to
>>>>have 2 or 3 sub column families within a single column family???I
>>>>want to store xml data in Hbase and I have sub tags that may go down
>>>>to 2 or 3 levels.
>>>>
>>>>Regards,
>>>>    Mohammad Tariq
>>>>
>>>
>>>
>
>



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