How big is each of the tables - are they all fairly small or fairly large? Small as in no more than thousands of rows or large as in tens of millions or hundreds of millions of rows?
Small tables are are not ideal for a Cassandra cluster since the rows would be spread out across the nodes, even though it might make more sense for each small table to be on a single node. You might want to consider a model where you have an application layer that maps logical tenant tables into partition keys within a single large Casandra table, or at least a relatively small number of Cassandra tables. It will depend on the typical size of your tenant tables - very small ones would make sense within a single partition, while larger ones should have separate partitions for a tenant's data. The key here is that tables are expensive, but partitions are cheap and scale very well with Cassandra. Finally, you said "10 clusters", but did you mean 10 nodes? You might want to consider a model where you do indeed have multiple clusters, where each handles a fraction of the tenants, since there is no need for separate tenants to be on the same cluster. -- Jack Krupansky On Tue, May 26, 2015 at 11:32 PM, Arun Chaitanya <chaitan64a...@gmail.com> wrote: > Good Day Everyone, > > I am very happy with the (almost) linear scalability offered by C*. We had > a lot of problems with RDBMS. > > But, I heard that C* has a limit on number of column families that can be > created in a single cluster. > The reason being each CF stores 1-2 MB on the JVM heap. > > In our use case, we have about 10000+ CF and we want to support > multi-tenancy. > (i.e 10000 * no of tenants) > > We are new to C* and being from RDBMS background, I would like to > understand how to tackle this scenario from your advice. > > Our plan is to use Off-Heap memtable approach. > http://www.datastax.com/dev/blog/off-heap-memtables-in-Cassandra-2-1 > > Each node in the cluster has following configuration > 16 GB machine (8GB Cassandra JVM + 2GB System + 6GB Off-Heap) > IMO, this should be able to support 1000 CF with no(very less) impact on > performance and startup time. > > We tackle multi-tenancy using different keyspaces.(Solution I found on the > web) > > Using this approach we can have 10 clusters doing the job. (We actually > are worried about the cost) > > Can you please help us evaluate this strategy? I want to hear communities > opinion on this. > > My major concerns being, > > 1. Is Off-Heap strategy safe and my assumption of 16 GB supporting 1000 CF > right? > > 2. Can we use multiple keyspaces to solve multi-tenancy? IMO, the number > of column families increase even when we use multiple keyspace. > > 3. I understand the complexity using multi-cluster for single application. > The code base will get tightly coupled with infrastructure. Is this the > right approach? > > Any suggestion is appreciated. > > Thanks, > Arun >
