December 22, 2010, 8:38 AM — There's always a sense of finally when a new version of Red Hat Enterprise Linux (RHEL) is released. We always know what's coming in the new OS, and generally we know when it'll be available, but we're still working with rapidly aging packages on the previous version and drumming our fingers for the next release.
With RHEL, the longer release cycle is the penalty to be paid for stability. When a new version of RHEL appears, it's been vetted for many moons through the cutting-edge Fedora Linux distribution. Presumably, most of the bugs have been worked out, but that doesn't help when you're busy shoehorning PHP 5.3 and MySQL 5.25 onto an RHEL 5.4 server.
The good news in RHEL 6 is a wealth of new features. These include very significant enhancements, long-awaited updates, and items that have been in place on other nominally less-stable distributions for months, if not years. After all, it's been nearly three years since RHEL 5.0 was released. The net result is that RHEL 6 is easily the best Red Hat Enterprise Linux release yet.
Given that RHEL 6 is composed of more than 2,000 software packages, there's no good way to fully test them all. But you can get a good sense of how an OS comes together simply by jumping in and configuring various services. By that measure, users familiar with Fedora and previous versions of RHEL will feel right at home. RHEL 6 drives much like RHEL 5.x does.
RHEL 6 hardware support First up are the enhancements to the core system. RHEL 6 defaults to the CFS (Completely Fair Scheduler) process scheduler and the usual CFQ (Completely Fair Queueing) I/O scheduler.
For x86_64 CPUs, RHEL 6 can natively support up to 128 cores and 2TB of RAM. Using other kernel extensions, those limits can be stretched to 4,096 cores and 64TB of RAM, if you're really pushing big iron. Naturally, this is thanks to the Linux 2.6.32 kernel.
Red Hat has also done plenty of work in optimizing memory management with NUMA, which can produce significant performance increases on larger systems.