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From Edward Capriolo <>
Subject Re: Multiple keyspace question
Date Tue, 10 Jul 2012 23:37:41 GMT
A problem of many keyspaces is clients are bound to a keyspace so
connection pooling multiple keyspaces is an issue. Cql has support for some
limited cross keyspace operations.

On Sunday, July 8, 2012, aaron morton <> wrote:
> 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
> 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 <>
> 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
> 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
> E
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> 2012/7/6 Ben Kaehne <>
> 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

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