image config

 <features>
        <acpi/>
    </features>
    <memory>MEMORY</memory>
    <vcpu>VCPUS</vcpu>
    <devices>
        <emulator>/usr/bin/kvm</emulator>
        <disk type='file'>
            <source file='BASEPATH/disk'/>
            <target dev='vda' bus='virtio'/> 
        </disk>
        <disk type='file'>
            <source file='BASEPATH/disk2'/>
            <target dev='vdb' bus='virtio'/> 
        </disk>
        <interface type='bridge'>
            <source bridge='BRIDGEDEV'/>
            <mac address='PRIVMACADDR'/>
            <model type='virtio'/>
        </interface>
        <serial type="file">
            <source path='BASEPATH/console.log'/>
            <target port='1'/>
        </serial>
        <graphics type='vnc' listen='' port=PORT passwd=PORT />
    </devices>

<domain type='kvm'>
    <name>i-4771079E</name>
    <os>
    <type>hvm</type>
        <kernel>/opt/awcloud/instance/admin/i-4771079E/kernel</kernel>
        <initrd>/opt/awcloud/instance/admin/i-4771079E/ramdisk</initrd>
        <cmdline>root=/dev/vda1 console=ttyS0</cmdline>
    </os>
    <features>
        <acpi/>
    </features>
    <memory>131072</memory>
    <vcpu>1</vcpu>
    <devices>
        <emulator>/usr/bin/kvm</emulator>
        <disk type='file'>
            <source file='/opt/awcloud/instance/admin/i-4771079E/disk'/>
            <target dev='vda' bus='virtio'/> 
        </disk>
        <disk type='file'>
            <source file='/opt/awcloud/instance/admin/i-4771079E/disk2'/>
            <target dev='vdb' bus='virtio'/> 
        </disk>
        <interface type='bridge'>
            <source bridge='awtoolbr10'/>
            <mac address='d0:0d:47:71:07:9E'/>
            <model type='virtio'/>
        </interface>
        <serial type="file">
            <source path='/opt/awcloud/instance/admin/i-4771079E/console.log'/>
            <target port='1'/>
        </serial>
        <graphics type='vnc' listen='' port='30000' passwd='30000' />
    </devices>
</domain>

利用virtio bus。因为SCSI emulation in kvm is not supported yet. In rhel 5.4 this is disabled. Use virtio drivers to enhance performance.