> - Do a lot of keyspaces cause some problems? (If I have 1,000 users, 
> cassandra creates 1,000 keyspaces…)
It's not keyspaces, but the number of column families. 

Without storing any data each CF uses about 1MB of ram. When they start storing 
and reading data they use more. 

IMHO a model that allows external users to create CF's is a bad one. 

Hope that helps.  
-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 25/05/2012, at 12:52 PM, Toru Inoko wrote:

> Hi, all.
> 
> I'm designing data api service(like cassandra.io but not using dedicated 
> server for each user) on cassandra 1.1 on which users can do DML/DDL method 
> like cql.
> Followings are api which users can use( almost same to cassandra api).
> - create/read/delete ColumnFamilies/Rows/Columns
> 
> Now I'm thinking about multitenant datamodel on that.
> My data model like the following.
> I'm going to prepare a keyspace for each user as a user's tenant space.
> 
> | keyspace1 | --- | column family |
> |(for user1)|  |
>               ...
> 
> | keyspace2 | --- | column family |
> |(for user2)|  |
>               ...
> 
> Followings are my question!
> - Is this data model a good for multitenant?
> - Do a lot of keyspaces cause some problems? (If I have 1,000 users, 
> cassandra creates 1,000 keyspaces...)
> 
> please, help.
> thank you in advance.
> 
> Toru Inoko.
> 

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