Generally, low number of C.F.s is better. Lower the number of C.F.s, better the performance. I am not sure if users go above 8 C.F.s. Most of the users keep number of C.F.s less than 4 or so. The implication of having more C.F.s and the density of those C.F.s in terms of data may vary, in that case it can cause unnecessary I/O burden when flushing or compacting.
Below link should help too: http://hbase.apache.org/book/number.of.cfs.html Setting compaction per C.F. is WIP https://issues.apache.org/jira/browse/HBASE-4770 Thanks, Jahangir. On Thu, Dec 29, 2011 at 12:01 AM, Rohit Kelkar <[email protected]>wrote: > 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 > >>> > >> > >> >
