What's new in Red Hat Enterprise Linux 6.2
by Thorsten Leemhuis
The enterprise distribution's second update of its sixth edition offers numerous optimisations for virtualisation, resource management and filesystems. New and improved drivers and a major X Server update enhance the distribution's hardware support.
Thirteen months after the introduction of Red Hat Enterprise Linux (RHEL) 6, Red Hat presented the second update to its Linux distribution for corporate customers on 6 December. As the RHEL 6 series is still in the first part of its life cycle, version 6.2 not only contains the fixes that have been approved since the introduction of RHEL 6.1, but also an extensive list of improvements.
Like the process scheduler of Linux 3.2, the RHEL kernel's scheduler now offers a "control group (cgroup) CPU ceiling enforcement" feature. This feature prevents applications within a cgroup from using more CPU resources than are allocated to this group, even if this means that available CPU resources remain unused. This is relevant, for example, in cloud environments with "pay-per-use" accessibility, because it prevents users from accessing more resources than they have purchased. Ceiling enforcement is also of interest for service level guarantees, to ensure that a user's purchased CPU resources are accessible in a guest system instantly and at any time.
Red Hat says that it has also improved the scalability of the cgroups code. According to the release notes, this will allow several hundred groups to be used without any performance implications. The Red Hat developers note that they have also improved the performance of the cgroup controllers for I/O tasks and for working memory.
The Linux 2.6.32-based RHEL kernel offers pstore, a feature that was integrated in Linux 2.6.39 and which allows crash analysis data to be stored in non-volatile memory in the event of a system crash; some recent systems include such "platform-persistent storage", which is a small memory area for storing this very information.
As usual, Red Hat has updated a whole range of drivers to support new hardware as well as hardware that is to be released in the coming months. A particularly large number of changes affect the storage and network hardware drivers; Red Hat highlights that they have improved the distribution's support for 10-Gigabit network hardware. The audio drivers, and those for USB 3.0 and PCI Express (PCIe), have also been updated.
Red Hat usually keeps the distribution's core components at the level of the version that is used when a RHEL family is first introduced. However, this time the Linux distributor has made an exception for the graphics stack, switching to version 7.11 of Mesa 3D and to version 1.10 of the X Server. The developers in that scope have updated the graphics drivers for AMD, Intel and NVIDIA hardware to improve the support for recent components. The release notes vaguely mention the provision of graphics support for Intel's next generation of chipsets, probably referring to the Ivy Bridge platform which is expected next year. An updated Synaptics touchpad driver adds multi-touch support.
Red Hat has raised the perf performance monitoring tool and its kernel-side components to the level of Linux 3.1, which, among other improvements, adds cgroup support.
Supported in the scope of the Scalable File System add-on of RHEL 6, the XFS filesystem has been improved to better handle metadata-intensive workloads – for instance when accessing a directory with a large number of small files, which, the release notes say, could previously cause degraded performance.
A new addition is the Parallel NFS (pNFS) architecture, which has been included as an unsupported Technology Preview. Specified as part of NFS 4.1, this technology is designed to significantly increase data throughput by processing metadata and data in parallel.
Ext4 filesystems can now be created much more quickly because the kernel uses "Lazy Inode Table Initialisation" and will only create some of the filesystem structures during formatting, while the remaining structures are built later on. Asynchronous data writes allow write operations via the CIFS filesystem to be executed up to twice as fast as before; the kernel uses CIFS to mount Samba and Windows shares. This improvement has recently also been integrated into the Linux main development branch and will be included in kernel version 3.2.