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From Mimi Aluminium <>
Subject Re: cluster size, several cluster on one node for multi-tenancy
Date Thu, 17 Feb 2011 19:34:11 GMT
I really need your help in this matter.
I will try to simplify my problem and ask specific questions

I am thinking of solving the multi-tenancy problem by providing a separate
cluster per each tenant. Does it sound reasonable?
I can end-up with one node belongs to several clusters.
Does Cassandra support several clusters per node? Does it mean several
Cassandra daemons on each node? Do you recommend doing that ? what is the
overhead? is there any link that explain how to do that?

Thanks a lot,

On Wed, Feb 16, 2011 at 6:43 PM, Mimi Aluminium <>wrote:

>  Hi,
> We are interested in a multi-tenancy environment, that may consist of up to
> hundreds of data centers. The current design requires cross rack and cross
> DC replication. Specifically, the per-tenant CFs will be replicated 6 times:
> in three racks,  with 2 copies inside a rack, the racks will be located in
> at least two different DCs. In the future other replication policies will be
> considered. The application will decide where (which racks and DC)  to place
> each tenant's replicas.  and it might be that one rack can hold more than
> one tenant.
> Separating each tenant in a different keyspace, as was suggested
> in  previous mail thread in this subject, seems to be a good approach
> (assuming the memtable problem will be solved somehow).
> But then we had concern with regard to the cluster size.
> and here are my questions:
> 1) Given the above, should I define one Cassandra cluster that hold all the
> DCs? sounds not reasonable  given hundreds DCs tens of servers in each DC
> etc. Where is the bottleneck here? keep-alive messages, the gossip, request
> routing? what is the largest number of servers a cluster can bear?
> 2) Now assuming that I can create the per-tenant  keyspace only for  the
> servers that in the three racks where the replicas are held,  does such
> definition reduces the messaging transfer among the other servers. Does
> Cassandra optimizes the message transfer in such case?
> 3) Additional possible solution was to create a separate clusters per each
> tenant. But it can cause a situation where one server has to run two or more
> Cassandra's clusters. Can we run more than one cluster in parallel, does it
> means two cassandra daemons / instances on one server? what will be the
> overhead? do you have a link that explains how to deal with it?
> Please can you help me to decide which of these solution can work or you
> are welcome to suggest something else.
> Thanks a lot,
> Mimi

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