What are the limitations of implementing MySQL NDB Cluster?
I want to implement NDB Cluster for MySQL Cluster 6. I want to do it for very huge data structure with minimum 2 million records.
I want to know is if there are any limitations of implementing NDB cluster. For example, RAM size, number of databases, or size of database for NDB cluster.
Answer
2 million databases? I asssume you meant "rows".
Anyway, concerning limitations: one of the most important things to keep in mind is that NDB/MySQL Cluster is not a general purpose database. Most notably, join operations, but also subqueries and range opertions (queries like: orders created between now and a week ago), can be considerably slower than what you might expect. This is in part due to the fact that the data is distributed across multiple nodes. Although some improvements have been made, Join performance can still be very disappointing.
On the other hand, if you need to deal with many (preferably small) concurrent transactions (typically single row updates/inserts/delete lookups by primary key) and you mangage to keep all of your data in memory, then it can be a very scalable and performant solution.
You should ask yourself why you want cluster. If you simply want your ordinary database that you have now, except with added 99,999% availability, then you may be disappointed. Certainly MySQL cluster can provide you with great availability and uptime, but the workload of your app may not be very well suited for the thtings cluster is good for. Plus you may be able to use another high availability solution to increase the uptime of your otherwise traditional database.
BTW - here's a list of limitations as per the doc: http://dev.mysql.com/doc/refman/5.1/en/mysql-cluster-limitations.html
But whatever you do, try out cluster, see if its good for you. MySQL cluster is not "MySQL + 5 nines". You'll find out when you try.