What to do on day two ~
On my second day I decided to read first and then watch some videos. I am reading: Welcome to Apache Cassandra 1.0 to see how this all started:http://www.datastax.com/wp-content/uploads/2011/09/WP-DataStax-Cassandra.pdf
One thing that immediately stands out, especially after my Hadoop experience, is that C* states there is “no single point of failure” for their system, based on Cassandra File System (CSF). That’s extremely important, as the HDFS High Availability (HA) features prove.
But Cassandra is not Hadoop, and CSF is not HDFS, so there is more detective work for me to do so that I can understand all these moving parts more clearly. After wading through the what is Cassandra (a best of breed new NoSQL database), I get into the technical details.
So, immediately Apache Cassandra solves the no failure problem by making all nodes identical. For those familiar with Hadoop, we had the NameNode and the JobTracker node, both of which were single points of failure. Thus the need for HDFS HA. With C* we can add nodes quite easily. How the automagical partitioning of the new node(s) occurs is not clear yet, but it will be.
Like Hadoop, C* also has the notion of data redundancy (or replication factor), which helps everyone sleep better at night. One promise about data replication that is new to me, is distribution between public cloud providers, or on-site data centers. That sounds great. This of course requires some configuration of a replication and data partitioning strategy up front, and then it just flies.
Another bit of news is that C* nodes communicate via the gossip protocol. Never heard of it. More research, be right back. Well, that was easy, our own DataStax docs explained that. Gossip is just a way that nodes share information, basically any given node shares its own state with up to three other nodes, and the rumors spread about who is who and what is what. It works — for both nodes added, and nodes that fail.
More soon, time for lunch.
Oh, and I decided to wait on watching the C* videos until I unpack my earphones, I just moved here to Half Moon Bay from Arizona, and I don’t want to disturb my colleagues as I learn. 😉