Red Hat Enterprise Linux 6.1
and Red Hat Summit 2011
by Thorsten Leemhuis
The first update to Red Hat Enterprise Linux 6 includes numerous KVM virtualisation-related enhancements. Some of the information contained in videos and presentation slides from this year's Red Hat and JBoss Summit may also be of interest to administrators of other distributions.
Six months after launching Red Hat Enterprise Linux (RHEL) 6, Red Hat has now released its first big update to the distribution. As is usual at this point in the seven to ten year life cycle of major RHEL releases, version 6.1, designated a minor release, is not limited to bug fixes and minor enhancements, but also includes a series of new functions. And, as ever, Red Hat has also updated many drivers to improve support for recently or soon to be released hardware.
There are a whole series of changes relating to virtualisation. The RHEL 6.1 kernel now includes vhost_net, which was added to the kernel in Linux 2.6.34. It moves some kernel network communication tasks to the kernel, reducing latencies and increasing throughput. Changes such as the addition of ioeventfd and various other enhancements should achieve a similar positive effect in the area of media access. Where qemu storage format qcow2 is used, metadata is now retained in RAM (metadata caching), which further improves I/O performance. Qcow2 now also supports live snapshots.
Source: redhat.com Pass through of PCI/PCIe devices to guest systems should now work with a greater range of hardware. KSM (Kernel SamePage Merging), which reduces memory usage, now supports transparent huge pages (THP), a technology for automatically using large memory pages which was merged into the standard Linux kernel at the start of this year. Red Hat also claims to have improved THP performance. The High Availability Add-On includes functions for KVM guest system failover handling. SPICE, a useful desktop virtualisation tool, can now pass through smartcard readers.
RHEL 6.1 includes many new and updated drivers for network, storage and graphics hardware. These include new 2D and 3D drivers for the graphics chip in Intel's new Sandy Bridge processors. Also new are the xorg-x11-drv-xgi driver, which addresses Z9S and Z11 series graphics chips, and support for the Matrox MGA-G200ER.
There is also full support for "hot adding" of processors and memory on systems which use Intel Xeon CPUs with Nehalem-EX cores and which support this feature. USB 3.0 is now officially supported – in version 6.0 this was still listed as a 'technology preview'.
The RHEL 6.1 kernel, which is based on Linux 2.6.32, now includes receive packet steering (RPS) and receive flow steering (RFS), which were merged into Linux kernel 2.6.35. Both use various tricks to increase network throughput and reduce latencies on multi-processor systems. Red Hat has also added the program biosdevname, which ensures that network names are consistent and predictable. Initially it will only be used by default on some Dell systems. NetworkManager now offers improved support for IPv6 and Wi-Fi Protected Access (WPA) Enterprise.
The RHEL 6.1 kernel now includes the autogroup scheduling feature merged into Linux 2.6.38, which improves the interactivity of desktop environments and applications in certain situations by automatically grouping all processes belonging to one session into a single group. In RHEL 6.1 autogroup scheduling is, however, disabled by default.
RHEL 6.1 now fully supports the creation of snapshots of mirrored logical volumes. LVM is also able to create a single logical volume which uses both striping and mirroring. Red Hat has significantly beefed up the functionality offered by control groups. Access to media can now be throttled, either by entering a throughput (bytes per second) or by limiting the number of input/output operations per second (IOPS). Cgsnapshot is a new feature which allows a backup snapshot of the cgroup configuration to be made.
Also new, though still at the technology preview stage for now, is the FreeIPA-based IPA (identity, policy and audit). IPA is a "security information management solution" which combines RHEL, Red Hat Directory Server, MIT Kerberos and NTP. More information is available in the Enterprise Identity Management Guide. Also at the technology preview stage, and thus not covered by the service contract, is the new Performance Application Programming Interface (PAPI), which allows the performance counters on modern processors to be used.
RHEL 6.1 contains Samba version 3.5.6 and Kerberos version 1.9. The boot loader should now work with disks which use 4 KB sector sizes on UEFI systems. The installer supports Emulex PCI-E Gen2 and Chelsio T4 10-gigabit Ethernet adapters. The distribution now displays a warning when installing on hardware which is not supported by Red Hat.
In parallel to the RHEL 6.1 launch, Red Hat is introducing a new Entitlement Platform to help manage the software inventory and entitlements for an organisation; the new Red Hat Subscription Manager manages the local system and its allocated subscriptions. The aim is to make installing and updating systems easier, and to simplify software compliance. Details can be found in the Installation Guide and Deployment Guide.
As part of its work on RHEL 6.1, Red Hat has also reworked and in some areas expanded the documentation for RHEL. There is a new V2V Guide, which describes how to import virtual machines created using KVM, VMware ESX or Xen into RHEL 6 using virt-v2v.
An easily digestible overview of all the changes in RHEL 6.1 can be found on the What's New web page. Greater technical detail can be found in the release notes, which include information on improved support for iSCSI and on cluster related changes. Even more detail can be found in the technical notes, which provide in depth descriptions of changes to individual RHEL components.
Background information and benchmarking results relating to some of the changes in 6.1 can also be found in the presentation slides, handouts and videos from some of the talks given at the recent Red Hat Summit and JBoss World 2011 in Boston.