How is Cassandra not consistent but HBase is?

Question

While going through the reading materials of Cassandra and HBase I found that Cassandra is not consistent but HBase is. Didn't find any proper reading materials for the same.

Could anybody provide any blogs/articles on this topic?

Answer 1

Cassandra is consistent, eventually. Based in Brewer's theorem (also known as CAP theorem), distributed data systems can only guarantee to achieve 2 of the following 3 characteristics:

• Consistency.
• Availability.
• Partition tolerance.

What this means is that Cassandra, in its default configuration, can guarantee to be available and partition tolerant, and there may be a delay before achieving consistency. But this is configurable, as you can increase the consistency levels for any query, sacrificing partition tolerance.

There are multiple resources in the web, you should look up for "eventual consistency in Cassandra", you can start with Ed Capriolo's talk, or this post in quora