The kernel in Red Hat Enterprise Linux 6.6 has been enhanced to enable user space to respond to certain SCSI Unit Attention conditions received from SCSI devices via the udev event mechanism. The supported Unit Attention conditions are:

Because SCSI Unit Attention conditions are only reported in response to a SCSI command, no conditions are reported if no commands are actively being sent to the SCSI device.

Red Hat Enterprise Linux 6.6 does not provide any default udev rules for these events, but user-supplied udev rules can be written to handle them. For example, the following rule causes a SCSI device to be rescanned if the inquiry data changes:

ACTION=="change", SUBSYSTEM=="scsi", ENV{SDEV_UA}=="INQUIRY_DATA_HAS_CHANGED", TEST=="rescan", ATTR{rescan}="x"

The rules for the supported events should match on the following SDEV_UA environment strings:

ENV{SDEV_UA}=="INQUIRY_DATA_HAS_CHANGED"
ENV{SDEV_UA}=="CAPACITY_DATA_HAS_CHANGED"
ENV{SDEV_UA}=="THIN_PROVISIONING_SOFT_THRESHOLD_REACHED"
ENV{SDEV_UA}=="MODE_PARAMETERS_CHANGED"
ENV{SDEV_UA}=="REPORTED_LUNS_DATA_HAS_CHANGED"

Note that in all cases the DEVPATH environment variable in the udev rule is the path of the device that reported the Unit Attention. Also, multipath I/O currently verifies that multiple paths to a device have some of the same attributes, such as the capacity. As a consequence, automatically rescanning a device in response to a capacity change can cause that some paths to a device have the old capacity and some paths have the new capacity. In such cases, multipath I/O stops using paths with the capacity change.

Red Hat Enterprise Linux 6.6 includes the Open vSwitch kernel module as an enabler for Red Hat's layered products. Open vSwitch is supported only in conjunction with products that contain the accompanying user-space utilities. Please note that without these required user-space utilities, Open vSwitch will not function and cannot be enabled for use. For more information, please refer to the following Knowledge Base article: https://access.redhat.com/knowledge/articles/270223.

Starting with Red Hat Enterprise Linux 6.6, the High Performance Networking (HPN) Add-On is no longer be available as a separate product. Instead, the functionality found in the HPN Add-On has been integrated into the base product and delivered as part of the Red Hat Enterprise Linux base channel.

In addition to including the HPN functionality into the base Red Hat Enterprise Linux 6 product, the RDMA over Converged Ethernet (RoCE) implementation has also been updated. RoCE uses Global Identifier or GID-based addressing for node-to-node communication. Previously, GIDs were encoded based on the Ethernet interface's MAC address along with the VLAN ID (if used). Under certain circumstances, the compute entity that runs the RoCE protocol is not aware that its traffic is VLAN-tagged. The compute entity can then sometimes create or assume a wrong GID, which can result in connectivity problems. The updated RoCE implementation resolves this problem by changing the way the RoCE GIDs are encoded, and instead bases them off the IP addresses of the Ethernet interface. All systems that use the RoCE protocol need to be upgraded to Red Hat Enterprise Linux 6.6 to ensure connection reliability due to this change in the wire protocol format.

Please refer to this Red Hat Knowledge Base article for additional information: https://access.redhat.com/site/articles/971333.

The scap-security-guide package has been included in Red Hat Enterprise Linux 6.6 to provide security guidance, baselines, and associated validation mechanisms that use Security Content Automation Protocol (SCAP). SCAP Security Guide contains the necessary data to perform system security compliance scans regarding prescribed security policy requirements; both a written description and an automated test (probe) are included. By automating the testing, SCAP Security Guide provides a convenient and reliable way to verify system compliance on a regular basis.

New hyperv-daemons packages have been added to Red Hat Enterprise Linux 6.6. The new packages include the Hyper-V KVP daemon, previously provided by the hypervkvpd package, the Hyper-V VSS daemon, previously provided by the hypervvssd package, and the hv_fcopy daemon, previously provided by the hypervfcopyd package. The suite of daemons provided by hyperv-daemons are needed when a Linux guest is running on a Microsoft Windows host with Hyper-V.

Several significant enhancements to device-mapper have been introduced in Red Hat Enterprise Linux 6.6:

The device-mapper-persistent-data package now provides tools to help use the new dm-era device mapper functionality released as a Technology Preview. The dm-era functionality keeps track of which blocks on a device were written within user-defined periods of time called an era. This functionality allows backup software to track changed blocks or restore the coherency of a cache after reverting changes.

Red Hat Enterprise Linux 6.6 provides support for Load Balancer technology with Keepalived and HAProxy.

Keepalived provides simple and robust facilities for load balancing and high availability. The load-balancing framework relies on the well-known and widely used Linux Virtual Server kernel module providing Layer-4 (transport layer) load balancing. Keepalived implements a set of checkers to dynamically and adaptively maintain and manage a load balanced server pool according to their health. Keepalived also implements the Virtual Router Redundancy Protocol (VRRPv2) to achieve high availability with director failover.

HAProxy is a TCP/HTTP reverse proxy which is particularly suited for high availability environments. HAProxy can:

Broadwell-U PCH SATA, HD Audio, TCO Watchdog, and I2C (SMBus) device IDs have been added for the drivers, which enables support for the next generation mobile platform in Red Hat Enterprise Linux 6.6.

Red Hat Enterprise Linux 6.6 adds the i40e and i40evf kernel drivers, which enable support for Intel X710 and XL710 family Ethernet adapters. These drivers are provided as Technology Preview only.

Added functionality of System Security Services Daemon (SSSD) enables better interoperability of Red Hat Enterprise Linux clients with Active Directory, which makes identity management easier in Linux and Windows environments. The most notable enhancements include resolving users and groups and authenticating users from trusted domains in a single forest, DNS updates, site discovery, and using NetBIOS name for user and group lookups.

A set of Apache modules has been added to Red Hat Enterprise Linux 6.6 as a Technology Preview. The Apache modules can be used by external applications to achieve tighter interaction with Identity Management beyond simple authentication.

The gdk-pixbuf2 package, previously a part of the gtk2 package, has been added to Red Hat Enterprise Linux 6.6. The gdk-pixbuf2 package contains an image-loading library that can be extended by loadable modules for new image formats. The library is used by toolkits such as GTK+ or Clutter. Note that downgrading the libraries included in the gdk-pixbuf2 and gtk2 packages can fail.

Performance Co-Pilot (PCP) provides a framework and services to support system-level performance monitoring and management. Its light-weight, distributed architecture makes it particularly well-suited to centralized analysis of complex systems.

Performance metrics can be added using the Python, Perl, C++ and C interfaces. Analysis tools can use the client APIs (Python, C++, C) directly, and rich web applications can explore all available performance data using a JSON interface.

For further information, consult the extensive man pages in the pcp and pcp-libs-devel packages. The pcp-doc package installs documentation in the /usr/share/doc/pcp-doc/* directory, which also includes these two free and open books from the upstream project:

http://www.performancecopilot.org/doc/pcp-users-and-administrators-guide.pdf

http://www.performancecopilot.org/doc//pcp-programmers-guide.pdf

Red Hat Enterprise Linux 6.6 features the java-1.8.0-openjdk packages, which contain the latest version of the Open Java Development Kit, OpenJDK8, that is now fully supported. These packages provide a fully compliant implementation of Java SE 8 and may be used in parallel with the existing java-1.7.0-openjdk packages, which remain available in Red Hat Enterprise Linux 6.6.

Java 8 brings numerous new improvements, such as Lambda expressions, default methods, a new Stream API for collections, JDBC 4.2, hardware AES support, and much more. In addition to these, OpenJDK8 contains numerous other performance updates and bug fixes.

Red Hat Software Collections is a Red Hat content set that provides a set of dynamic programming languages, database servers, and related packages that you can install and use on all supported releases of Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7 on AMD64 and Intel 64 architectures.

Dynamic languages, database servers, and other tools distributed with Red Hat Software Collections do not replace the default system tools provided with Red Hat Enterprise Linux, nor are they used in preference to these tools. Red Hat Software Collections uses an alternative packaging mechanism based on the scl utility to provide a parallel set of packages. This set allows for optional use of alternative package versions on Red Hat Enterprise Linux. By using the scl utility, users can pick and choose which package version they want to run at any time.

Red Hat Developer Toolset is now a part of Red Hat Software Collections. It is included as a separate Software Collection. Red Hat Developer Toolset is designed for developers working on the Red Hat Enterprise Linux platform. It provides current versions of the GNU Compiler Collection, GNU Debugger, Eclipse development platform, and other development, debugging, and performance monitoring tools.

See the Red Hat Software Collections documentation for the components included in the set, system requirements, known problems, usage, and specifics of individual Software Collections.

See the Red Hat Developer Toolset documentation for more information about the components included in this Software Collection, installation, usage, known problems, and more.