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Virtualization
The following Virtualization updates are also included in this release:
AMD-V is now supported in this release. This enables live domain migration for fully
virtualized guests.
The in-kernel socket API is now expanded. This was done to fix a bug that occurs when
running sctp between guests.
Virtual networking is now part of libvirt, the virtualization library. libvirt has a set of
commands that sets up a virtual NAT/router and private network for all local guests on a
machine. This is especially useful for guests that do not need to be routable from the
outside. It is also useful for developers who use Virtualization on laptops.
Note that the virtual networking capability adds a dependency on dnsmasq, which handles
dhcp for the virtual network.
For more information about libvirt, refer to http://libvirt.org.
libvirt can now manage inactive virtual machines. libvirt does this by defining and
undefining domains without stopping or starting them. This functionality is similar to the
virsh define and virsh undefine commands.
This enhancement allows the Red Hat Virtual Machine Manager to display all available
guests. This allows you to start these guests directly from the GUI.
Installing the kernel-xen package no longer leads to the creation of incorrect / incomplete
elilo.conf entries.
The xm create command now has a graphical equivalent in virt-m anager.
Nested Paging (NP) is now supported. This feature reduces the complexity of memory
management in virtualized environments. In addition, NP also reduces CPU utilization in
memory-intensive guests.
At present, NP is not enabled by default. If your system supports NP, it is recommended that
you enable NP by booting the hypervisor with the parameter hap=1.
Shared Page Tables
Shared page tables are now supported for hugetlb memory. This enables page table entries
to be shared among multiple processes.
Sharing page table entries among multiple processes consumes less cache space. This
improves application cache hit ratio, resulting in better application performance.
Installing to dm-multipath Devices
Anaconda now has the capability to detect, create, and install to dm-multipath devices. To
enable this feature, add the parameter mpath to the kernel boot line.
This feature was originally introduced in Red Hat Enterprise Linux 5 as a Technology Preview,
and is now fully supported in this release.
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4. Release Notes for ppc
Note that dm -multipath also features inbox support for the Dell MD3000. However, multiple
nodes that use dm-m ultipath to access the MD3000 cannot perform immediate failback.
Further, it is recommended that you use the Custom Partitioning interface in Anaconda if
your system has both multipath and non-multipath devices. Using Automatic Partitioning in
such cases may create both types of devices in the same logical volume groups.
At present, the following restrictions apply to this feature:
If there is only one path to the boot Logical Unit Number (LUN), Anaconda installs to the
SCSI device even if m path is specified. Even after you enable multiple paths to the boot
LUN and recreate the initrd, the operating system will will boot from the SCSI device
instead of the dm -multipath device.
However, if there are multiple paths to the boot LUN to begin with, Anaconda will correctly
install to the corresponding dm-m ultipath device after m path is specified in the kernel
boot line.
By default, user_friendly_nam es is set to yes in m ultipath.conf. This is a required
setting in the support implementation of the dm -m ultipath root device. As such, setting
user_friendly_nam es to no and recreating the initrd will result in a boot failure with
the following error:
Checking filesystems
fsck.ext3: No such file or directory while trying to open
/dev/mapper/mpath0p1
Booting from Storage Area Network (SAN)
The ability to boot from a SAN disk device is now supported. In this case, SAN refers to a Fibre
Channel or iSCSI interface. This capability also features support for system-to-storage
connection through multiple paths using dm -multipath.
In configurations that use multiple host bus adapters (HBA), you may need to set the system
BIOS to boot from another adapter if all paths through the current adapter fail.
Driver Update Program
The Driver Update Program (DUP) was designed to allow third-party vendors (such as OEMs)
to add their own device drivers and other Linux Kernel Modules to Red Hat Enterprise Linux 5
systems using regular RPM packages as the distribution containers.
Red Hat Enterprise Linux 5.1 applies several updates to the DUP, most notably:
install-time Driver Update RPMs through Driver Update Disks is now supported
bootpath Driver Updates affecting the system bootpath are now supported
support for third-party packaging of Advanced Linux Sound Architecture (ALSA) is now
deprecated
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