If you are using the Virtual Server 2005 SP1 Beta (details here: http://blogs.technet.com/megand/archive/2005/04/20/403950.aspx) one of the new additions is a F6 driver floppy.  This is located under the Virtual Server installation directory “Virtual Machine Additions” and is called “SCSI Shunt Driver.vfd”.  You can use this floppy during the early stages of Windows installation (when you are prompted to hit ‘F6’ to load any custom drivers) to install Windows using our optimized SCSI driver as opposed to the generic Adaptec driver.

For most users this will make a small difference in install times (approximately 10%) – but for some users it will make a significant difference.

Some users have reported that Windows installation under Virtual Server while using the emulated SCSI controller can take up to 6 to 24 hours.  These users are usually running physical systems that have physical SCSI hard disks in them as well.  The problem is that it appears that these physical SCSI disks have very poor performance for small read and write commands (but excellent performance for large read and write commands).  By default the generic Adaptec driver used inside of Virtual Server heavily utilizes small reads and writes.  For users who have seen this problem – using the F6 driver floppy should bring operating system install times back down to approximately 1 hour.
Cheers,
Ben