For the last two and a half years, Oracle has been selling its own supported version of Linux based on Red Hat Enterprise Linux (RHEL).
But the company claims it’s not a fork.
That’s an important distinction for Oracle (NASDAQ: ORCL), which makes billions from its products running on Linux, and is a very active player in the open source OS’s ecosystem.
Instead, Oracle has long maintained that its Linux distribution, Oracle Enterprise Linux, includes changes simply to enable the company to better provide support to customers. It also said its changes get contributed to the upstream Linux community, and that its distribution is binary-compatible with RHEL, which means that software certified to run on Red Hat’s OS will run similarly on Oracle Enterprise Linux.
“A lot of people think Oracle is doing Enterprise Linux as just basically a rip off of Red Hat, but that’s not what this is about,” Wim Coekaerts, director of Linux engineering at Oracle, told InternetNews.com. “This is about a support program, and wanting to offer quality Linux OS support to customers that need it. The Linux distribution part is there just to make sure people can get a freely available Linux operating system that is fully supported.”
“We don’t want to create a new Linux distribution that is different from Red Hat, because the issue is about support and not the software itself,” Coekaerts added.
Yet, as it turns out, Oracle Enterprise Linus’s binary compatibility does not mean that its version is entirely identical to Red Hat’s. In fact, there are some important differences, including support for a key file system technology.
Differences, but not a fork
Oracle isn’t the only vendor with a RHEL clone. CentOS, for instance, is a popular community-based clone of Red Hat’s Enterprise Linux as well.
While the CentOS community aims to make RHEL freely available to the masses, Oracle maintains that its motivation centers around support, which it delivers through two Linux support programs.
The Oracle Unbreakable Linux program provides support to customers who already have Linux installed, while the Oracle Enterprise Linux support offering is supposed to be an exact replica of RHEL, and provides the software to users. Oracle offers that version because RHEL isn’t available for free as a complete operating system without a Red Hat subscription.
To Oracle, the differences between its distribution and Red Hat’s aren’t about creating a wholly new direction for Linux. Instead, it said it contributes its code back upstream.
“All the new features that we work on to make Linux a strong operating system go to Linus Torvalds and they become part of the mainline Linux kernel,” Coekaerts said. “Then that trickles back down to the distribution vendors and then we can make use of the feature.”
Page 2: OCFS and differences in virtualization
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Oracle has said the approach means it can work on enhancing Linux without creating its own version of the OS. The only issue, though, is that not everything that Oracle gets into the mainline Linux kernel is actually used by all the distribution vendors, including Red Hat.
One example of how Oracle’s supported version of Linux differs from Red Hat has to do with the Oracle Cluster File System (OCFS), which has been part of the mainline Linux kernel since the Linux 2.6.16 release in 2006.
Though it’s part of the mainline Linux kernel, it is not included in Red Hat’s Enterprise Linux, where it would compete against Red Hat’s own Global File System (GFS).
Oracle, however, provides support for OCFS and offers it to its customers.
“Since Red Hat compiles OCFS out of its kernel, we actually build the modules that you can download separately,” Coekaerts explained. “So, we don’t have to recompile the kernel. On our Linux server, we add the OCFS [packages], so you can pull in the extra packages and they will work on both RHEL and Oracle Enterprise Linux the same.”
Coekaerts added that Oracle fully supports OCFS, and argued that a good number of customers came to Oracle for Linux support because they want to use OCFS.
He noted that OCFS support is not an extra cost to Oracle subscribers, and in his view, it does not affect Oracle’s compatibility or certification with Red Hat.
Red Hat, however, doesn’t see a similar need for OCFS.
Nick Carr, Red Hat’s marketing director, said that there are a number of shared disk file systems for Linux, and that Red Hat has been delivering GFS for several years.
“It is included in the upstream kernel and is integrated with storage virtualization technologies,” Carr told InternetNews.com.
“At this time, Red Hat has received minimal customer demand for OCFS,” he added. “However, we regularly evaluate all the available Linux file systems as part of our strategy to deliver best-of-breed solutions to our customers. As of today, we believe that GFS is the best shared disk file system for our customers.”
Xen vs. KVM
Another area where Red Hat and Oracle differ is on their view of virtualization technology. Currently, both Red Hat and Oracle use the Xen open source virtualization technology, though Red Hat has publicly stated its intentions to move to the rival KVM virtualization technology.
Red Hat bought out KVM vendor Qumranet in 2008 for $107 million.
Oracle has its own flavor of Xen, called OracleVM, and it’s not something that it plans on moving away from anytime soon.
“OracleVM is our product, so we’re not dependent on Red Hat’s choice, and whether they use KVM or Xen doesn’t affect us,” Coekaerts said. “We’re happy with the solution we have, and going forward, we know that it will work really well for Oracle.”