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From Norman Maurer <>
Subject Re: cluster size, several cluster on one node for multi-tenancy
Date Thu, 17 Feb 2011 19:44:32 GMT
Maybe you could make use of "Virtual Keyspaces".

See this wiki for the idea:


2011/2/17 Frank LoVecchio <>:
> 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 <>
> wrote:
>> 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
>>> 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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