For starters, 5.3 beefs up virtualization, enabling virtualization to run on larger systems with more memory and with more guests per host. According to Daniel Riek, an RHEL product manager, the number of processors in RHEL 5.3 beta nearly doubled from 64 to 126, and memory per host has nearly quadrupled from 256 GB to a 1 TB. In addition, the 5.3 beta enables each guest server to connect to at least four network devices. The beta version actually tested 16 network interface connectors per guest, enabling each guest server to connect to as many as 16 networks or eight high-availability networks.
With these enhancements to RHEL, companies will be able to virtualize large, complex applications that have simultaneous linkage to many disk storage or network devices which, in turn, will enable them to virtualize more applications and workloads, Riek said.
In addition, virtualization performance has improved by optimizing the RHEL OS for Intel's new virtual memory Extended Page Tables (EPT), which translates guest physical addresses to host physical addresses in hardware, greatly speeding the translation process and, in turn, reducing virtualization overhead, Riek said. Intel's EPT performs this process far faster than in software but EPT required modification of the OS to support Intel's changes, he said. Collectively, EPT -- along with physical-to-virtual drivers -- accelerates virtualization as much as 30 times, boosting performance of a virtual machine to levels near those on bare metal, he said.
RHEL has also improved integration of paravirtualized drivers for the open source Xen hypervisor, which will speed disk and network traffic, he said. For the first time, RHEL has added Xen drivers for Windows similar to those it includes for VMware, he said. Windows drivers are currently in beta and nearly final, he said.
In addition, the new beta 5.3 version includes the Global File System, or GFS2, an upgraded cluster file system on RHEL's Advanced Platform. In 2003, GFS1 was incorporated from Red Hat's acquisition of Sistina. The new version has been redesigned for bigger systems so it handles larger files, recovers faster and provides easier user access, he said. The file system check capability has also been improved, he said.
Finally, there are numerous additional features included in the beta release as a technology preview. These features are offered for community review and feedback but are not yet supported. One is SystemTap utrace support, which, like Sun Microsystems' dtrace tool, enables users to measure an application's performance and pinpoint bottlenecks. Previously, RHEL users could only track internal operations in the kernel; now they can do the same with applications, he said.
The technology preview also includes a VMware ESX cluster fence agent, which enables RHEL guests to be clustered on VMware, as well as the new ext4 Linux file system (an incremental update to the current ext3). Finally, it includes Kerberos-based single sign-on that enables Linux users to access distributed file systems through Windows Active Directory, he added.
Overall, 5.3 beta is significant because it coordinates OS improvements with the latest hardware to optimize performance, Riek said. With hardware vendors now focusing on new features rather than just adding more powerful processors with new releases, the optimization process is more complicated, he said.
"The hardware and the OS need to be updated together in order to get the benefit of the new features," Riek said. "That's why it's so important that they are tested together to get the value to customers."
The production-ready version of RHEL 5.3 is expected sometime in January, he said.Clear strides, but nothing earth-shattering
Gordon Haff, a principal IT adviser at Nashua, N.H.-based Illuminata Inc., described the 5.3 beta as an incremental, relatively minor release, which he said is to be expected at this stage of Linux's lifespan.
Point releases tend to involve tweaking code, making minor changes that are important to someone or to supporting the latest hardware modifications, he said. One exception, however, is virtualization, and RHEL 5.3's improvements reflect that.
For example, RHEL 5.3 beta can now run as a guest on the KVM hypervisor -- the virtualization technology acquired by Red Hat in September 2008 -- which enables developers to test it, even though KVM won't officially be added to RHEL until at least the next full release.
Nevertheless, despite clear strides in virtualization. "RHEL 5.3 is a minor release," Haff said. "At this point, the low-hanging fruit is mostly gone."