6. Virtualization

6. Virtualization

This section contains information about updates made to Red Hat Enterprise Linux suite of Virtualization tools.

Enhancements/Updates
  • Running 16 cores or more using AMD Rev F processors no longer results in system resets when performing fully-virtualized guest installations.

  • On an AMD NPT system used as a PAE host, guests can now have more than 4GB of memory.

    Note that nested paging can only translate 32-bit guest virtual addresses. This is because of a hardware feature that exists only in 32-bit physical address extensions (PAE).

  • When entering the second stage of a Windows™ Server 2003 installation, you no longer need to manually edit /etc/xen/[name of guest machine] to continue. The current user interface now allows you to change media on CD-ROMs attached to the guest.

  • The Virtual Machine Manager (virt-manager) included in this release now allows users to specify kernel boot parameters to the paravirtualized guest installer.

  • During the lifetime of dom0, you can now create guests (i.e. xm create) more than 32,750 times.

  • When using virt-manager to add disks to an existing guest, duplicate entries are no longer created in the guest's /etc/xen/[domain name] configuration file.

Known Issues
  • Paravirtualized guests can only have a maximum of 16 disk devices.

  • Migrating paravirtualized guests through xm migrate [domain][dom0 IP address] does not work.

  • Repeated live migration of paravirtualized guests between two hosts may cause one host to panic. If a host is rebooted after migrating a guest out of the system and before migrating the same guest back, the panic will not occur.

  • When installing Red Hat Enterprise Linux 5 on a fully virtualized SMP guest, the installation may freeze. This can occur when the host (dom0) is running Red Hat Enterprise Linux 5.2.

    To prevent this, set the guest to use a single processor using the install. You can do this by using the --vcpus=1 option in virt-install. Once the installation is completed, you can set the guest to SMP by modifying the allocated vcpus in virt-manager.

  • If a system configured for kdump encounters a kernel panic while an IDE device is performing I/O, the system may be unable to successfully boot into the kdump environment. This occurs if the IDE device is controlled by a device driver other than libata, and is caused by a bug in the IDE/ATA driver stack.

    To work around this, use the kdump command-line argument hd[X]=noprobe for storage devices and hd[X]=cdrom for optical drives, where [X] is the device identifier. Either command-line argument should be added to KDUMP_COMMANDLINE_APPEND in /etc/sysconfig/kdump.