Virtualization Technology News and Information
What's New in Red Hat Enterprise Linux 6.2

On December 6th, a little over the one-year anniversary of Red Hat Enterprise Linux 6 availability, Red Hat released Red Hat Enterprise Linux 6.2. As with every minor release, Red Hat Enterprise Linux 6.2 consolidates all patches, enhancements and security updates from the previous Red Hat Enterprise Linux release (6.1 in May 2011). As always, Red Hat maintains certified application compatibility, ISV and IHV support and testing for all releases.

Red Hat Enterprise Linux 6.2 delivers dramatic improvements in resource management and high availability, new features aimed at storage and file system performance, identity management functionality, and technology integration with VMware and Microsoft environments.

The key benefits for organizations deploying Red Hat Enterprise Linux 6.2 are higher levels of efficiency realized through resource management and performance optimization, along with enhanced business agility through additional security enhancements and more flexibility for virtualized and clustered environments.

Virtualization and Cloud Support

Scalability, Performance, and More Efficient Management

More efficient management with cgroups

Processor ceilings improvements with cgroups

  • Red Hat Enterprise Linux 6.2 now provides the ability to set upper limits for CPU consumption to better manage SLAs, especially for multi-tenant environments – this new feature provides better overall control of CPU allocation.
  • The task scheduler in the Linux kernel (referred to as Completely Fair Scheduler or CFS) tries to allocate processor time proportionately between all the groups of tasks. This can often result in a task group getting more than its share of processor time if there are idle cycles available thus setting upper limits for consumption can better control allocation. 
  • Service Providers can now set maximums for CPU time associated with a virtual machine which allows them to better manage SLAs without having to “give away” CPU resources. (This capability already exists for memory.)

cgroup CPU controller

Improved scalability

  • Lower overhead realized through cgroups, provides more efficient and better scaling for higher levels of guest consolidation.
  • Control Groups, cgroups, are used to create and manage slices of computing resources for specific processes and can be used as part of SLA management. Large SMP systems that are hosting multiple tenants or processes need to be finely divided without limits. Enhancements in Red Hat Enterprise Linux 6.2 now provides the ability to create 100’s of control groups and provide system administrators with very fine-grained control over their environment.
  • System administrators now can to provision their servers at a very fine grain, making it easier to achieve very high system utilization rates for 100’s of processes/tenants with no degradation of overall system performance. This is ideal for tightly managing SLAs.

cgroup I/O controller for improved performance

  • The I/O controller within the cgroup framework performs better as a result of more efficient use of locks inside the kernel.
Red Hat Enterprise Virtualization 3.0 
  • Red Hat Enterprise Virtualization 3.0, currently in beta, will benefit from the performance, scalability, hardware enablement, KVM hypervisor enhancement, and advanced technologies enabled by Red Hat Enterprise Linux 6.2.
  • Red Hat’s Enterprise Virtualization provides a complete infrastructure for managing hundreds f physical hosts and thousands of virtual machines running Red Hat Enterprise Linux or Microsoft Windows guests for server and desktop virtualization use cases. More  information about the Red Hat Enterprise Virtualization 3.0 can be found at 
KVM Updates

Virtual CPU timeslice sharing for multiprocessor guests

  • Virtual CPU timeslice sharing for multiprocessor guests is a new feature in Red Hat Enterprise Linux 6.2. Scheduler changes within the kernel now allow for virtual CPUs inside a guest to make more efficient use of the timeslice allocated to the guest, before processor time is yielded back to the host. This change is especially beneficial to large SMP systems that have traditionally experienced guest performance lag due to inherent lock holder preemption issues. In summary, this new feature eliminates resource consuming system overhead so that a guest can use more of the CPU resources assigned to them much more efficiently.
  • CPU resources allocated to a guest can be partially consumed due to pre-emption, especially in multi-socket systems. Red Hat Enterprise Linux 6.2 was enhanced to ensure a guest to minimize pre-emption and use as much of the CPU resources allocated to them before the guest hits its pre-determined CPU limits.
  • Guests will now use more of the CPU resources assigned to them which will increase the efficiency of the guest and the overall system by eliminating some resource-consuming system overhead.

Network performance improvements with KVM

  • KVM network performance is a critical requirement for Virtualization and cloud-based products and solutions. Improvements have been made in KVM to more efficiently process a variety of workloads that generate small (less than 4K) messages. New functionality added has significantly reduced networking related CPU utilization on the host on which the guest is located.
  • In addition, network drivers in KVM (virtio-net) have been enhanced to process UDP traffic faster. This is achieved with the help of more efficient UDP checksum validation. Also in cases where the UDP checksum has been validated by the host, it is not necessary to also validate in the guest KVM guests no longer validate the UDP checksum if that action has been performed by the host NIC.

Guest debugging configuration

  • The ability to configure guests for debugging, while already present in KVM, is now available via the libvirt API and the virsh command line tool. This functionality enables an easier method of debugging virtualized guests and simplifies virtualization administration. It is now possible to trigger non-maskable interrupts (NMI) or initiate a back trace to debug guest environments.

Pre-boot guest environment auditing

  • IT administrators want the ability to audit and monitor their virtualized environments, from creation to runtime and retirement. Red Hat Enterprise Linux 6.2 now enables administrators the ability to monitor and audit the entire boot sequence including the boot process before a guest is actually booted. This is achieved using the newly introduced sgabios component and the existing virsh console.

Guest memory pinning KVM

  • Bare-metal systems have enjoyed the ability to pre-assign, a.k.a., pin down CPUs and memory in NUMA systems for the greatest performance and minimal delays due to waiting for these resources to be freed up. Prior Red Hat Enterprise Linux releases allowed CPU pinning in virtualized guests. With the added capability to pin down memory in KVM, this same capability has now been delivered for virtualized environments, delivering greater performance for critical virtualized workloads.

Linux Containers

  • Linux containers provide a flexible approach to application runtime containment on bare-metal without the need to fully virtualize the workload. This release provides application level containers to separate and control the application resource usage policies via cgroup and namespaces. This release introduces basic management of container life-cycle by allowing for creation, editing and deletion of containers via the libvirt API and the virt-manager GUI.
  • Linux Containers provides a means to run applications in a container, a deployment model familiar to UNIX administrators. Also provides container life-cycle management for these containerized applications through a graphical user interface (GUI) and user space utility (libvirt).
  • Linux Containers is in Technology Preview at this time.   

To find out what else is new in RHEL 6.2:

Red Hat Enterprise Linux 6.2 What’s New Technical Features and Benefits document:
Red Hat Enterprise Linux 6.2 press release here

Published Thursday, December 08, 2011 3:12 PM by David Marshall
Filed under:
What's New in Red Hat Enterprise Linux 6.2 : … | Linux - V??e o Linuxu - (Author's Link) - December 8, 2011 6:22 PM
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