[libvirt-users] shutdown a windows guest take ages..... (20- 34 minutes here)

hi, i use libvirt 1.0.2 (-r1 , gentoo linux). when i create a vm with win7 guest, virtio nic, virtio hdd, all is running fine. but when i shutdown the windows guest, it takes somestimes 20-34 minutes !!! iotop shows me in the whole time writing with 2,xxmb/sec. is the complete machine "rewritten" to disk? i use disk.images on a raid6, but hey, dd shows me it can writes there with 26mb/sec. any ideas what causes these long shutdown times? thanks for any hints, marko