Field Report: eHarmony Finds a Compatible Database

As the lovelorn search for soul mates on eHarmony.com, the matching of those well-advertised "29 dimensions of compatibility" across more than 17 million registered users drives as many 1,200 transactions per second.

Business has been booming for the five-year-old dating site, with an average of 10,000 new users filling out its compatibility survey each day. As business grew, however, the company's relationship with its database, Microsoft SQL Server 2000, was on the rocks. By mid 2005, when the site hit peak loads — mostly on Sunday, Monday and holiday nights — the eight-CPU, dual-core machines running the OLTP database would often hit 100-percent CPU utilization.

"We needed more capacity, and there was no way to do it other than to move onto a more scalable database," says Mark Douglas, vice president of technology. "Federating our data into multiple data sets just wasn't an attractive alternative."

The issue wasn't data volume, which now tops out at a mere 4 terabytes, it was the sheer transactional demand. "I've talked to people who manage much larger databases, but they're only doing 30,000 transactions per day," says Douglas. "We handle that many transactions in about 30 seconds."

eHarmony.com had other complaints about the database, such as frequent planned outages and read locking, so rather than upgrade to SQL Server 2005, which had yet to be released when the company made its decision, eHarmony sought greener pastures in an Oracle stack including Oracle Database 10g, Oracle Real Application Clusters (RAC), Oracle Clusterware and Oracle Enterprise Manager 10g on multiple Sun Fire X4600 servers running Windows.

More than anything else, Douglas says it was the promise of Oracle RAC that wooed eHarmony. "Oracle was a more scalable database for us," says Douglas. "We can put it against more machines in a cluster, and it had more enterprise-class features like partitioning."

Indeed, Oracle has led the way in bringing clustering to the database, with Sybase recently becoming only the second database vendor to offer this scalability-enhancing feature.

It took 14 months for eHarmony.com to migrate to the Oracle infrastructure, and when it finally made the switch last December, site performance improved by 30 percent to deliver "sub-second response," says Douglas.

As long as it was switching databases for OLTP, eHarmony.com decided to migrate its data warehouse to Oracle as well. "SQL Server was performing just fine for the warehouse, but once you change the source production system, it's just much easier to keep it all with one vendor."

As for eHarmony's jilted database, Douglas says there are no hard feelings. "It's all about performance and availability," he says. "SQL Server performed very well for the company for many years. It was just getting to a point where we needed certain features, like clustering, that Microsoft couldn't offer."