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From David McNelis <dmcne...@agentisenergy.com>
Subject Re: For multi-tenant, is it good to have a key space for each tenant?
Date Fri, 07 Oct 2011 14:47:00 GMT
So at the end of the day its going to be limited by available memory then?
 Going by this line:

Do note that a minimum of 1MB per memtable is used by the per-memtable arena
allocator <https://issues.apache.org/jira/browse/CASSANDRA-2252> also
introduced in 1.0, which is worth keeping in mind if you are looking at
going from thousands to tens of thousands of ColumnFamilies.

  Then you'd be looking at a requirement of 1gig  memory for each  1024
column families had on your cluster, regardless of number of keyspaces those
lived in.  So in order to have 10s of thousands of CFs, one would need 10s
of gigs of ram on each node just to handle that overhead...at least as  of
 v1.

On Fri, Oct 7, 2011 at 9:40 AM, Jonathan Ellis <jbellis@gmail.com> wrote:

> On Fri, Oct 7, 2011 at 9:36 AM, David McNelis
> <dmcnelis@agentisenergy.com> wrote:
> > In some documentation I've read it says that
> > keyspace's take up the majority of the resources
>
> This has never been the case.
>
> > in a couple of older
> > threads they talked about getting the number of column families down.
>
> This was good advice pre-0.8.
>
> I covered the state of 0.8 and 1.0 here:
>
> http://www.datastax.com/dev/blog/whats-new-in-cassandra-1-0-improved-memory-and-disk-space-management
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of DataStax, the source for professional Cassandra support
> http://www.datastax.com
>



-- 
*David McNelis*
Lead Software Engineer
Agentis Energy
www.agentisenergy.com
o: 630.359.6395
c: 219.384.5143

*A Smart Grid technology company focused on helping consumers of energy
control an often under-managed resource.*

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