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Saturday, January 1, 2011

KVM & Virtio (disk/nic) on Scientific Linux 6 (alpha 3) « Xen Virtualization on Linux and Solaris

KVM & Virtio (disk/nic) on Scientific Linux 6 (alpha 3)

KVM as a “full virtualization” is a nice feature because it allows you to run any operating system virtualized. However, it’s relatively slow because the hypervisor has to emulate actual physical devices such as RTL8139 network cards and the most recent SeaBios emulates IDE interface.This fragment from KVM guest dmesg log is fair enough :-

[ 0.129740] ata_piix 0000:00:01.1: version 2.13
[ 0.129802] ata_piix 0000:00:01.1: setting latency timer to 64
[ 0.129954] scsi0 : ata_piix
[ 0.130522] scsi1 : ata_piix
[ 0.130552] ata1: PATA max MWDMA2 cmd 0x1f0 ctl 0x3f6 bmdma 0xc000 irq 14
[ 0.130554] ata2: PATA max MWDMA2 cmd 0x170 ctl 0x376 bmdma 0xc008 irq 15

Virtio is a Linux standard for network and disk device drivers where just the guest’s device driver “knows” it is running in a virtual environment, and cooperates with the hypervisor. This enables guests to get high performance network and disk operations, and gives most of the performance benefits of paravirtualization.
If you want to install a machine with virtio drivers you should add these lines to your virt-install command:

--os-type=linux \
--os-variant=virtio26 \

Using this command you enable the virtio drivers at install time on SL 6 (alpha 3)

# virt-install –connect qemu:///system -n UDSK10.10 -r 2048 –vcpus=2 \



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