I would do a test to see the latency difference under load between having 1 KS with 5 CF's and 50 KS with 5 CF's.
Your test will need to read and write to all the CF's. Having many CF's may result in more frequent memtables flushes. (Personally it's not an approach I would take.) Cheers ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 7/07/2012, at 8:15 AM, Shahryar Sedghi wrote: > Aaron > > I am going to have many (over 50 eventually) keyspaces with limited number of > CFs (5-6) do you think this one can cause a problem too. > > Thanks > > On Fri, Jul 6, 2012 at 2:28 PM, aaron morton <aa...@thelastpickle.com> wrote: > Also, all CF's in the same KS share one commit log. So all writes for the row > row key, across all CF's, are committed at the same time. > > Some other settings, such as caches in 1.1, are machine wide. > > If you have a small KS for something like app config, I'd say go with > whatever feels right. If you are talking about two full "application" KS's I > would think about their prospective workloads and growth patterns. Will you > always want to manage the two together ? > > Cheers > > ----------------- > Aaron Morton > Freelance Developer > @aaronmorton > http://www.thelastpickle.com > > On 6/07/2012, at 9:47 PM, Robin Verlangen wrote: > >> Hi Ben, >> >> The amount of keyspaces is not the problem: the amount of column families >> is. Each column family adds a certain amount of memory usage to the system. >> You can cope with this by adding memory or using generic column families >> that store different types of data. >> >> With kind regards, >> >> Robin Verlangen >> Software engineer >> >> W http://www.robinverlangen.nl >> E ro...@us2.nl >> >> Disclaimer: The information contained in this message and attachments is >> intended solely for the attention and use of the named addressee and may be >> confidential. If you are not the intended recipient, you are reminded that >> the information remains the property of the sender. You must not use, >> disclose, distribute, copy, print or rely on this e-mail. If you have >> received this message in error, please contact the sender immediately and >> irrevocably delete this message and any copies. >> >> 2012/7/6 Ben Kaehne <ben.kae...@sirca.org.au> >> Good evening, >> >> I have read multiple keyspaces are bad before in a few discussions, but to >> what extent? >> >> We have some reasonably powerful machines and looking to host an additional >> (currently we have 1) 2 keyspaces within our cassandra cluster (of 3 nodes, >> using RF3). >> >> At what point does adding extra keyspaces start becoming an issue? Is there >> anything special we should be considering or watching out for as we >> implement this? >> >> I could not imagine that all cassandra users out there are running one >> massive keyspace, and at the same time can not imaging that all cassandra >> users have multiple clusters just to host different keyspaces. >> >> Regards. >> >> -- >> -Ben >> >> > > > > > -- > "Life is what happens while you are making other plans." ~ John Lennon
