I use libvirt to attach a volume to xen's guest VM,but l got the following message:

 

Attached device: /dev/sdb
[Mon Jul  4 09:18:58 2011][006640][EUCAERROR ] libvirt: Requested operation is not valid: Xm driver only supports modifying persistent config (code=55)
[Mon Jul  4 09:18:58 2011][006640][EUCAERROR ] AttachVolume() failed (err=-1) XML=<disk type='block'><driver name='phy'/><source dev='/dev/sdb'/><target dev='sdae'/></d
isk>
[Mon Jul  4 09:18:58 2011][006640][EUCAERROR ] ERROR: doAttachVolume() failed error=1
[Mon Jul  4 09:19:02 2011][006640][EUCADEBUG ] doDescribeResource() invoked
[Mon Jul  4 09:19:02 2011][006640][EUCADEBUG ] doDescribeInstances() invoked