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From Frank LoVecchio <>
Subject Re: cluster size, several cluster on one node for multi-tenancy
Date Thu, 17 Feb 2011 19:37:55 GMT
Why not just create some sort of ACL on the client side and use one
Keyspace?  It's a lot less management.

On Thu, Feb 17, 2011 at 12:34 PM, Mimi Aluminium

> Hi,
> 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,
> Mimi
> 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

Frank LoVecchio
Senior Software Engineer | Isidorey, LLC
Google Voice +1.720.295.9179 | |

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