FWN/Beats/Virtualization

Virtualization

In this section, we cover discussion on the @et-mgmnt-tools-list, @fedora-xen-list, @libvirt-list and @ovirt-devel-list of Fedora virtualization technologies.

Contributing Writer: Dale Bewley

Enterprise Management Tools List

This section contains the discussion happening on the et-mgmt-tools list

New Release virt-manager 0.6.1

Cole Robinson announced[1] a new virt-manager release, version 0.6.1.

This release includes:

• VM disk and network stats reporting (Guido Gunther)
• VM Migration support (Shigeki Sakamoto)
• Support for adding sound devices to an existing VM
• Enumerate host devices attached to an existing VM
• Allow specifying a device model when adding a network device to an existing VM
• Combine the serial console view with the VM Details window
• Allow connection to multiple VM serial consoles
• Bug fixes and many minor improvements.

[1] http://www.redhat.com/archives/et-mgmt-tools/2009-January/msg00067.html

New Release virtinst 0.4.1

Cole Robinson announced[1] a new virtinst release, version 0.4.1.

This release includes:

• Add virt-image -> vmx support to virt-convert, replacing virt-pack (Joey Boggs)
• Add disk checksum support to virt-image (Joey Boggs)
• Enhanced URL install support: Debian Xen paravirt, Ubuntu kernel and boot.iso, Mandriva kernel, and Solaris Xen Paravirt (Guido Gunther, John Levon, Cole Robinson)
• Expanded test suite
• Numerous bug fixes, cleanups, and minor improvements

[1] http://www.redhat.com/archives/et-mgmt-tools/2009-January/msg00068.html

Fedora Virtualization List

This section contains the discussion happening on the fedora-virt list.

Fedora Xen List

This section contains the discussion happening on the fedora-xen list.

Xen Users Shafted on Fedora?

Evan Lavelle wondered[1] if those who have invested years in Xen on Fedora have been "shafted". "Xen isn't flavour of the month around here, but I assumed there were good reasons for that. Now, rather belatedly, I've found" that Red Hat acquired (FWN #143[Z]) Qumranet and KVM.

Neil Thompson thought[4] not. "Shafted?...I don't think so. We're just in a blip at the moment." Pointing out that "RHEL5, which has a number of years left, includes xen - I don't think Red Hat are going to mess their corporate clients around by removing it. The problem with F8 is that the kernel people could no longer drag an obsolete (2.6.21) kernel around just for xen, and decided to concentrate on helping get it into the mainstream kernel. This has taken longer than expected."

Jan ONDREJ was also concerned[2] that, "KVM is still not a replacement for paravirtualized machines and I think fully virtualized KVM will be slower like a paravirtualized XEN."

Richard W.M. Jones countered[3] "KVM is a great replacement for Xen. It's much easier to use for a start -- no more rebooting into a completely separate kernel hypervisor. As long as you have the virtio[4] drivers in the guest, which is the default for all new Linux distros, performance is roughly the same."

Apropros to the topic, but on another list, Mark McLoughlin explained[7] "Para-virtualization isn't always better.

KVM uses full virtualization, meaning that it uses the processor's support for virtualization. This means you can run an unmodified guest OS on KVM.

If you can modify the guest OS, then KVM does allow you to use paravirtualization for some performance sensitive operations - so e.g. we've got pvclock, pv MMU and virtio devices.

Don't get tied up in marketing terminology - try both and decide for yourself which works best for you."

[1] http://www.redhat.com/archives/fedora-xen/2009-January/msg00031.html

[Z] http://fedoraproject.org/wiki/FWN/Issue143#Red_Hat_Acquires_Makers_of_KVM.2C_Qumranet_Inc.

[2] http://www.redhat.com/archives/fedora-xen/2009-January/msg00032.html

[3] http://www.redhat.com/archives/fedora-xen/2009-January/msg00041.html

[4] http://www.redhat.com/archives/fedora-xen/2009-January/msg00033.html

[5] http://www.redhat.com/archives/fedora-xen/2009-January/msg00035.html

[6] http://www.redhat.com/archives/fedora-xen/2009-January/msg00038.html

[7] http://www.redhat.com/archives/et-mgmt-tools/2009-January/msg00063.html

Migrating Xen DomU to KVM Guest

Migrating a virtual machine from Xen to KVM is straight forward. Well, more or less.

Richard W.M. Jones explained[3] how to migrate from Xen to KVM

• Ensure recent kernel in guest with

"Install a recent Linux kernel in the guest, adjust the configuration file[1], and reboot. You only need xenner if you want to run the Xen PV guest unchanged (ie. without installing a new guest kernel).

[1] 'virsh edit domname', and edit the domain type, <os> and <emulator> fields, as detailed here: http://libvirt.org/drvqemu.html"

And[5] detailed how to take advantage of speedy virtio drivers in the guest. "You have to tell the host to give the guest a virtio network card - change the NIC <model type='virtio'/> as described here: http://libvirt.org/formatdomain.html#elementsNICS

The guest needs to have a relatively up to date kernel which has drivers for the virtio network card - that's included in all recent Linux kernels (virtio_net.ko)."

Richard finally noted[6] "Upgrading to using virtio_blk is very complicated. You have to rebuild initrd, and there's a difficult circular dependency to be resolved when doing this because you need to be using virtio_blk in order for mkinitrd to believe that you need it, although possibly mkinitrd supports some command line argument to override this. I actually gave up at this point.

For newly installed guests, recent anaconda just works everything out for you and puts the correct drivers into initrd."

Mark McLoughlin distilled this into the mkinitrd command in the guest:

mkinitrd --with virtio_pci --with virtio_blk -f /boot/initrd-$(kernelversion) $(kernelversion)

"You only need to do this once. After that, if a new kernel is installed while you're booted off a virtio disk, then mkinitrd will include the modules automatically. "

Emre Erenoglu elaborated[8] "You will also need to specify /dev/vdX on the kernel root= line and make sure your init script inside your initrd triggers the virtio drivers at boot so that the /dev/vdX are created."

Template:Admin/Warning Mark McLoughlin added[9] a caveat. "Could this have been an x86_64 Fedora 9 xen guest? If so, you probably hit a nasty special case - the F9 x86_64 xen kernel didn't have support for running 32 bit binaries like grub, so the bootloader would never have been installed into the MBR. That works fine for pygrub, but not with KVM's real BIOS."

[3] http://www.redhat.com/archives/fedora-xen/2009-January/msg00041.html

[4] http://wiki.libvirt.org/page/Virtio

[5] http://www.redhat.com/archives/fedora-xen/2009-January/msg00048.html

[6] http://www.redhat.com/archives/fedora-xen/2009-January/msg00053.html

[7] http://www.redhat.com/archives/fedora-xen/2009-January/msg00054.html

[8] http://www.redhat.com/archives/fedora-xen/2009-January/msg00058.html

[9] http://www.redhat.com/archives/fedora-xen/2009-January/msg00078.html

Libvirt List

This section contains the discussion happening on the libvir-list.

oVirt Devel List

This section contains the discussion happening on the ovirt-devel list.