The Brangelina of Big Data: Cassandra mates with Hadoop

Horses for Big Data courses

DataStax was founded by a pair of former Rackspace employees, Jonathan Ellis and Matt Pfeil, who had worked on Cassandra at the Texas hosting provider. Ellis is the chair of the Apache Cassandra project, and DataStax is a Red Hat-like effort to commercialize the platform.

Ben Werther bills the company as an outfit that provides software, support, and services for the open source database. It does not provide its own Cassandra distro, but it plans to offer a for-pay enterprise version of the platform. Yes, it's eying the "open core" model favored by companies such as Eucalyptus or Cloudera. Currently, it offers a management and monitoring tool for Cassandra known as OpsCenter. Customers include Netflix, OpenWave, Cisco, and Rackspace.

With Brisk, it's trying something new, hoping to out-Hadoop Hadoop. "Hadoop does many great things," Werther says. "The core MapReduce capabilities are very strong. People love Hive and its SQL-like design. But the HSFS file system is very complex to set up, has single points of failure, and – according to feedback from our customers – is just not ready to do what they want it to do.

"Cassandra can serve all of the functions of that lower level part of the Hadoop stack, but at the same time give you low-latency realtime application capabilities in that same infrastructure."

What's more, he says, Cassandra is designed in such a way that you can have part of your Brisk infrastructure focus on analytics while another handles low-latency applications. "You can use it as a realtime infrastructure as you write queries in Hive, and as you right things back with Hive, they're immediately available to the application."

As described by DataStax, Brisk contrasts with what Facebook has done on its own backend. When Facebook built its new email-meets-IM-meets-everything else messaging system, it did not build atop Cassandra. It chose HBase, the open-source distributed database the mimics BigTable atop the Hadoop HDFS file system.

In a recent Facebook "tech talk" broadcast on the net, Facebook infrastructure guru Karthik Ranganathan said that Cassandra's "eventual consistency" model wasn't up to the task and that system required the "strong consistency" model used by HBase. When a user sends an email, he said, you have to be able to tell the user – without delay – that the email was sent.

Plus, Facebook was already using Hadoop, and HBase is specifically designed to dovetail with the platform. Hadoop MapReduce now spans a petabyte-scale cluster inside the company. "MapReduce is so useful," Ranganathan said. "It's like the air you breathe."

DataStax has gone the opposite way, pairing Cassandra with Hadoop. "HBase is less mature than Cassandra," Werther says. "And it's built on HDFS, which has scalability and reliability challenges." No doubt, some will agree. Even within Facebook, some engineers question why the company didn't stick with Cassandra for messaging, and the company heavily modify HBase before it was ready for the live service.

But you can be sure that many others with take the other stance, backing HBase over Brisk.

DataStax says that several of its existing customers actually requested a platform along the lines of Brisk. The platform is suited not only to high-volume websites, according to Werther, but also financial services firms and retail outfits. "You can have an application that is receiving a stream of market data, reacting and predicting, maintaining a realtime view to what's going on," he says. "But your infrastructure can also store data for historical use, letting you run queries on what has happened."

At the moment, this is little more than talk. The platform has not been used on production systems. It hasn't even been open-sourced. But one way or another, it's a head-turning proposition. ®