Oracle RAC on VMware gets no support from Oracle

Oracle will not support customers running Oracle RAC on VMware, for reasons that many say are political and technically outdated.

The software company’s reasoning behind the position is largely nonexistent. According to an unofficial Oracle site, Oracle RAC on VMware is supported in “only very specific circumstances.” Meanwhile, the My Oracle Support metalink on VMware indicates that Oracle RAC is not supported on VMware at all. Oracle did not answer requests for comment on this story.

Count David Robbins as one of the confused. A database administrator at Reed Elsevier, a Europe-based publishing company best known for its LexisNexis subsidiary, Robbins said his company runs Oracle RAC as its standard, using it “mainly for high availability.”

“We run a 24/7 website and have customers around the world, so downtime is really not acceptable,” he said.

At the same time, there is a push within the company to virtualize everything. With virtualization, deployment and user provisioning are quicker and easier, Robbins said. But with Oracle not supporting Oracle RAC on VMware, he can’t justify it.

“If we have a production outage, we can’t go to Oracle and have them say they’re not supporting it because it’s on VMware,” he said. “That’s just a situation we can’t put ourselves in.”

Both Oracle RAC and virtualization are growing technologies, according to a SearchOracle.com reader survey this year. Almost 60% of respondents are using virtualization or plan to do so in the next year, and clustering adoption has increased 10% in the last two years. In addition, VMware is by far the preferred virtualization vendor, running in three-quarters of Oracle shops running virtualization.

Why Oracle won’t support RAC on VMware

Oracle’s tepid support of single-instance Oracle Database on VMware is now fairly well known. In short, Oracle won’t support it unless the customer can prove that the problem wasn’t related to the virtual machine.

That was one of the reasons why Bob Storey, DBA at the Davidson County Sheriff’s office in Tennessee, wouldn’t do it. Storey said that server administrators wanted to move to VMware and were insistent that Oracle would run fine there. Storey said he wouldn’t even consider it until Oracle supported it better.

“You first had to prove that it was not an issue with regard to the VM, which meant blowing the virtual machine back out to physical,” Storey said. “My issue with that was that once you blew it out to the physical, you changed the variables involved.”

While getting support for single-instance Oracle on VMware is difficult, getting it for Oracle RAC on VMware is practically impossible. Oracle hasn’t officially explained why it won’t support RAC on VMware, but it has told customers a few things.

First is the so-called “clock drift” issue. This happens when running Oracle RAC on VMware on top of Linux. Simply put, older versions of the Linux kernel did not account for virtualization because its designer didn’t anticipate it. As a result, the way the physical hardware keeps time could get out of sync with the way the virtual machine guest running Oracle RAC was keeping time. For an Oracle RAC DBA who is inserting rows in databases and having them time-stamped, that could cause a problem. Rows on RAC Instance A, for example, could be a minute off from rows on RAC Instance B, causing table corruption.

Customers have also heard that Oracle is concerned about brownouts when running Oracle RAC on VMware. In particular, there are concerns that if VMware doesn’t provide the same level of hardware resources that the full hardware would, then RAC could start shutting down virtual machines and cause a brownout.

Dave Welch, chief technology officer at House of Brick, an Omaha, Neb.-based Oracle consultancy, said both situations are no longer issues in reality. Regarding clock drift, he said, newer Linux kernels sync the clock, Oracle Database 11g R2 has a time sync feature, and VMware now has tools to sync the time. Regarding brownouts, Welch said he’d never seen it actually happen in a live environment with his customers.

“We’ve dealt with both of them,” he said. “Two years ago, the clock drift issue was very real. Today, it’s moot. It’s a paper tiger.”

Beyond the technical issues, pretty much everyone outside Oracle says it’s also a political matter. Oracle wants to own the entire IT stack, from the hardware to the application, and that includes the virtualization layer. For example, the company published a 37-page white paper last month about running Oracle RAC on Oracle VM, its own virtualization platform. But when it comes to running Oracle RAC on VMware, the most popular virtualization technology today, Oracle is mostly silent.

Trying to push customers toward Oracle VM won’t always work. Such is the case with Robbins of Reed Elsevier.

“VMware is our standard. We’re not going to run Oracle VM,” he said. “Our sys admins say they know VMware, and we’re not bringing in another virtual solution.”

Oracle RAC also represents “significant revenue” for the company despite being a small percentage of the installed base, Oracle president Charles Phillips said in a quarterly earnings call last year. If Oracle supported RAC on VMware, that could mean customers might run their cluster on less hardware, which could mean decreasing their processor-based Oracle licensing costs. That could mean less money for Oracle.

Robbins feels as if he’s stuck between a rock and a hard place.

“I would think they want to keep their customers happy. But other than that, I don’t know if there’s a benefit to them supporting it,” he said. “It’s not like we’re going to stop using Oracle.”

Mark Fontecchio can be reached at [email protected].