Hey there
Using qemu-kvm libvirt-bin virt-manager
I’ve seen some very poor I/O performance with virtio enabled
installing an guest debian lenny 64bit took 45min
at install I’ve seen some very heavy disk load
So we need to enable this in libvirt:
virsh edit blahguest
and put that into the line “driver”
cache='writeback'
<disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='writeback'/> <source file='/var/lib/libvirt/images/blahguest.qcow2'/> ..... ..... </disk>
Never need to set this with debian lenny using libvirt or kvm directly
I think something changed in linux-kvm code
Have fun