Red Hat launches Enterprise Linux 6

Wednesday's launch of Red Hat Enterprise Linux 6 was a kind of non-event event.

If it's hard to make a server operating system announcement exciting, it is perhaps even more difficult to make it predictable, or almost boring. But that's what commercial Linux distributor Red Hat has tried to do for the last decade, and in its own way tame the open source Linux kernel (and the surrounding code that makes it an operating system) so that commercial and government entities would trust it.

That's not a slam — and Red Hat would not take it that way, either. That's because the current RHEL 5 version will continue to get hardware and security updates for many years in its ten-year support lifecycle, so no one is being forced to march directly to RHEL 6 today.

More importantly, RHEL 5 is good enough for most customers in terms of performance and scalability that they don't have to move to RHEL 6, unlike earlier commercial-grade Linuxes from SUSE/Novell or Canonical, the early releases of Microsoft's Windows in the late 1990s, or the early releases of any of the Unixes two decades ago.

You were ready to get out on the bleeding edge in the early years of these platforms because the upside outweighed the risks. In today's commercial Windows, Unix, and Linux worlds, the platforms are mature and customers can calmly plan their upgrades over the span of years. And that is exactly what Red Hat expects them to do as they pay their annual license fees for Linux subscriptions no matter if they are on RHEL 4, 5, or 6.

That said, RHEL 6 represents a significant improvement in performance, scalability, reliability, and power management compared to its predecessor. And therefore, like any new operating system version, RHEL 6 merits some enthusiasm and attention.

We do run our businesses on these things, after all.

At Wednesday's RHEL 6 launch event in San Francisco, Jim Totten, general manager and vice president of the platform business unit at Red Hat, said that the RHEL 6 stack included some 1,821 customer and partner feature requests and took more than 600 person-years to put together over the past several years.

Since it went into beta in the spring, Totten said, Red Hat's software engineers have squashed 14,631 bugs reported by partners, customers, and reports from the open source community that may be using RHEL but not paying for support contracts.

The RHEL 6 stack includes 2,058 packages, which is an 85 per cent increase over RHEL 5 — not that you tell the quality of the stack by the number of programs in it. But, to be fair, this also means that there is a much larger number of programs that fall under the Red Hat support, and choice is always better. Red Hat doesn't think it can raise its support prices by 85 per cent, which is good for customers.

Paul Cormier, president of products and technologies at Red Hat and Totten's boss, didn't like a question at the event asking if Red Hat was winning the kernel race against Oracle and CentOS for its own operating system, and downplayed the whole idea of looking at a release or version based on its kernel. "I don't think there is a kernel race," Cormier said. "Linux is way beyond what versions of the kernel or DNS server you are using," he explained. What matters, said Cormier, "is the roadmap we have customers on."

But just the same, Totten said that Red Hat engineers contributed 3,900 enhancements to the Linux 2.6.32 kernel, and added that RHEL 6 is based on this 2.6.32 kernel with many features pulled in from the more current 2.6.33 and 2.6.34 releases. Red Hat has been backporting kernel features and hardening them since Advanced Server with the Linux 2.4 kernel back in 2002, so this is not new behavior. (El Reg readers no doubt know of more and probably earlier examples. I merely point this out as a comparison.)

Like the prior RHEL 4 and RHEL 5 versions, RHEL 6 is supported on 32-bit x86 and 64-bit x64 platforms from Advanced Micro Devices and Intel as well as on IBM Power and mainframe platforms. While RHEL 4 and RHEL 5 supported Intel's Itanium processors, RHEL 6, as El Reg exclusively reported a year ago, does not run on Itanium systems.

According to the RHEL 6 datasheet, on 32-bit x86 platforms, RHEL 6 scales to 32 computing elements (cores, or threads if the processor has them, what are sometimes called virtual CPUs) and as much as 16GB of main memory. On 64-bit x64 platforms, it can scale to 128 cores/threads and 2TB of main memory using one set of kernel extensions and to 4,096 cores/threads and 64TB of main memory. (Not that anyone can build a system with that many processors or that much memory yet.)

On Power-based machines, RHEL 6 is not scaling as far as IBM's iron does, and only supports 128 cores/threads and 2TB of memory; the top-end Power 795 supports 256 cores, 1,024 threads, and 8TB of memory. On the System z platforms, you are limited to 64 cores and 1.5TB of memory on System z10 mainframes and 80 cores and 3TB of memory on the new System zEnterprise 196 machines announced in July.

Red Hat has put together a server version comparison table here so you can see how RHEL has evolved through its versions, and also has created a more detailed technical capabilities table spanning the desktop and server editions as well.

Some other feeds and speeds: the embedded version of the KVM hypervisor that ships with RHEL 6 can support a guest OS that spans 64 virtual CPUs and 256GB of virtual memory with a 64-bit guest operating system. The default file system with RHEL 6 is ext4, which can scale up to 16TB. With a storage add-on module, Red Hat is supporting the XFS and GFS2 file systems, which both can scale up to 100TB.

At the launch event, Totten said that Red Hat had expended a lot of effort in making the non-uniform memory access (NUMA) clustering features of the Linux kernel sit up and bark, with large memory optimizations and the addition of transparent hugepages. With these and other enhancements to the KVM hypervisor, not only can RHEL 6 demonstrate linear scalability as CPU cores or threads are added to a box, but the performance penalty for running a workload was on the order of 10 to 15 percent running virtualized instead of on bare metal. (Red Hat used the Stream memory benchmark test on four-socket Xeon 7500 server to prove this.) It also showed that just turning on the new NUMA features on a standard SMP machine with 8, 16, or 32 cores or threads can have a significant affect on performance — on the order of 20 to 40 per cent on larger machines.

Totten also bragged about the energy efficiency improvements that come with RHEL 6 after making lots of changes in the kernel and the stack to allow for hardware to be quiesced when it is not needed.

Red Hat was able to show a 20 per cent reduction in idle power consumption on a two-socket Xeon 5500 server moving from RHEL 5.4 to RHEL 5.5 (from 145 watts down to 110 watts), and says that just loading RHEL 6 on this box will lower the idle power consumption by another 20 per cent to around 80 watts, in large part because of the tweaking in the tickless Linux kernel variant, but also due to power management on other system features.

Totten said that RHEL 6 has a number of different power profiles that allow customers to quickly select how aggressive they want to be on power settings and then automatically set all the software switches to make this happen. (You can, of course, make your own settings manually.)

There's a slew of new features in RHEL 6. One interesting one for servers is that it allows for the hot addition of processors and main memory. The IPv6 networking stack is also supported, and so is the Apache 2.2 Web server and Memcached 1.4.4.

The RHEL 6 stack includes the GCC 4.4 compiler set, has compatibility libraries for RHEL 4 and 5, and includes the OpenJDK 6 implementation of the Java Standard Edition runtime and the Tomcat 6 application server. The RHEL 6 stack also has Ruby 1.8.7 and Rails 3 if you want to work on that railroad all the live-long day, as well as PHP 5.3.2 and Perl 5.10.1. On the database front, the stack includes PostgreSQL 8.4.4, MySQL 5.1.47, and SQLite 3.6.20.

Red Hat has changed the packaging and pricing model for RHEL with version 6, and El Reg is analyzing that now to give you the scoop. Stay tuned. ®