why do you think so? I'll let users create ristricted CFs, and limit a number of CFs which users create.
is it still a bad one?
Ok, get it, you want to limit the cf user can create (assume) 2, what about 10k shared users creating 2 cf each=> 20k CF ~~20GB memory used with no data in it. Do you think it is good one?

 I can think of your data model like , S3 or shared hosting is limit Keysapce and cf to fixed number.
In Cassandra key and column name is very powerful, you can do anything you want, design DM anyway you want.
Here is the approach I probably will take.

                     /* user1 profile*/
  } ,
                     /* user2 profile*/
  } ,


                     /* user1 activity columns here*/
  } ,
                     /* user2 activity columns here*/
  } ,

marker cf that will keep all unique  signature fro users. So it can be queried while creating new one.


problem with this approach is user may not have liberty to define their own data model. Good for fixed pattern data: logger, hits, geodata.



On Thu, 31 May 2012 06:44:05 +0900, aaron morton <aaron@thelastpickle.com> wrote:

- 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

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.

技術・品質・情報グループ 技術開発部

猪子 徹(Toru Inoko)
tel       : 03-6438-3544
mail      : inoko@ms.scsk.jp

With kind regards,

Robin Verlangen
Software engineer

W http://www.robinverlangen.nl
E robin@us2.nl

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