Hello! My config: Parallels Workstation 2.2 Host OS - Windows XP Pro SP2 Guest OS - Windows XP Pro SP2 As I can see in Device Manager of guest OS the Transfer mode is DMA 5. I had run HD Speed (http://www.steelbytes.com/?mid=20) inside VM and the result was 32-34 Mbyte/sec. This corresponds to DMA 2 mode. I had run VM on old PATA and new SATA HDDs and I'd got the same results. I had tested HD Speed inside Parallels Server VM and I'd got ~55Mbyte/sec on my old PATA HDDs and ~75 Mb/sec on my new SATA HDD. It seems to me there is a bug in Parallels Workstation.
