Twitter growth prompts switch from MySQL to 'NoSQL' database

By Eric Lai, Computerworld |  Software, database, nosql

Like Facebook and Twitter, Digg is also moving from MySQL , the initial Web 2.0 darling, to Cassandra.

Cisco Systems Inc., hosting provider Rackspace and other firms also use Cassandra. The largest Cassandra instance in production runs 100TB of data using 150 servers, according to the project's web site.

The interview was cited in a tweet from King, who has 297,334 Twitter followers.

In the blog intervirew, King said that Twitter looked at a number of options for upgrading its system, including re-architecting MySQL so that it runs better in a cluster (called 'sharding'), and the offerings of several Cassandra NoSQL rivals such as HBase, Voldemort, MongoDB, MemCacheDB, Redis and HyperTable.

King said that test found that Cassandra was more scalable, reliable and easier to manage than the alternatives.

Twitter is "currently moving our largest (and most painful to maintain) table -- the statuses table, which contains all tweets and retweets" to Cassandra, he said. "After this we'll start putting some new projects on Cassandra and migrating other tables."

To minimize downtime during the migration, Twitter plans to implement new features by running them in Cassandra alongside MySQL in case any bugs crop up. Once its determined there are no bugs, Twitter will back up MySQL data and then export it to Cassandra in a process that would take about a week, he said.

Only after more testing, will it turn Cassandra on for production and shut down MySQL.

"Our process for rolling out new major infrastructure can be summed up as 'integrate first, then iterate,' King said.

Eric Lai covers Windows and Linux, desktop applications, databases and business intelligence for Computerworld . Follow Eric on Twitter at @ericylai , send e-mail to elai@computerworld.com or subscribe to Eric's RSS feed .

Read more about databases in Computerworld's Databases Knowledge Center.


Originally published on Computerworld |  Click here to read the original story.
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