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" <[email protected]> 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 <[email protected]> >To: [email protected] >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 <[email protected]> >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 >> <[email protected]> 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" <[email protected]> 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 >>>> >>> >>> > >
