使用xml配置文件创建并启动虚拟机出错

配置文件如下：

<domain type='kvm'>
    <name>ubuntu12</name>            //the name of kvm
    <memory>1048576</memory>            //max Memory
    <currentMemory>1048576</currentMemory>      //usedable Memory
    <vcpu>1</vcpu>                //virtual CPU num
    <os>
       <type arch='x86_64'>hvm</type>
       <boot dev='cdrom'/>            //start width CDROM
    </os>
    <features>
       <acpi/>
       <apic/>
       <pae/>
    </features>
    <clock offset='localtime'/>
    <on_poweroff>destroy</on_poweroff>
    <on_reboot>restart</on_reboot>
    <on_crash>destroy</on_crash>
    <devices>
        <emulator>/usr/bin/kvm</emulator>
        <disk type='file' device='disk'>
            <driver name='qemu' type='raw'/>
            <source file='/home/yu/kvm_demo/demo/test.raw'/>
            <target dev='hda' bus='ide'/>
        </disk>
        <disk type='file' device='cdrom'>
             <source file='/home/yu/kvm_demo/demo/ubuntu-12.04.4-desktop-amd64.iso'/>
             <target dev='hda' bus='ide'/>
        </disk>
        <interface type='network'>
             <mac address="50:e5:49:22:70:1b"/>
             <source network='default' />
             <adress type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0' />
        </interface>
        <input type='mouse' bus='ps2'/>
         <graphics type='vnc' port='-1' autoport='yes' keymap='en-us'/>
     </devices>
</domain>

报错如下：

root@yu-H61M-D2-B3:/home/yu/kvm_demo/demo# vi setup.xml
root@yu-H61M-D2-B3:/home/yu/kvm_demo/demo# virsh define setup.xml
定义域 ubuntu12（从 setup.xml）

root@yu-H61M-D2-B3:/home/yu/kvm_demo/demo# virsh start ubuntu12
错误： 开始域 ubuntu12 失败
错误： internal error: process exited while connecting to monitor: qemu-system-x86_64: -drive file=/home/yu/kvm_demo/demo/ubuntu-12.04.4-desktop-amd64.iso,if=none,id=drive-ide0-0-0,readonly=on,format=raw: Duplicate ID 'drive-ide0-0-0' for drive
原因：

使用了两个hda，第二个要换成hdb。