Currently I'm using ESX (v3 and v4) to test a scripted OS (Windows 2003) and application install DVD. The DVD ISO (8GB) is mounted on a 1Gbps NFS datastore and the VMDK's (20GB) are on an SSD mounted via NFS over a 10Gbps link.
It still takes a lot longer than I'd really like for to run through a test iteration and I'm wondering if mounting the virtual disks and ISO on a RAM disk on the same server as the hypervisor is running on would be worth my while. I can dedicate a server to this VM and 32GB of RAM in the system should be adequate to do the trick I'd guess. (1GB hypervisor OS, 28GB RAM disk and 2GB for the VM is < the 32GB available to me)
Since hosting a RAM disk within ESX does not seem possible I'm open to trying KVM/Xen/Hyper-V. KVM would probably be my first choice of these three.
Anyone out there tried this? Bear in mind this is purely for a test run of the installer, the VM will be discarded as soon as the test is completed so I'm not worried about losing data from the remote possibility of a power failure.
I've done it with Hyper-V.
The result will be that your storage latency will drop to near zero, which will very much accelerate your scenario. Your total CPU usage will increase some, as the CPUs will be copying data around RAM, rather than telling a storage controller to do DMA.
It's not clear to me from your description whether you intend to clean-install the OS as part of your test or whether the OS can be pre-installed on the virtual hard disk. This will greatly affect the speed of the test, as the Hyper-V storage drivers won't be installed in Server 2003 until late in OS installation.
As a final note, Hyper-V will need a little bit more RAM. So you'll have to use sparse disks that don't actually eat up 20GB. I suspect your test will run even faster if you give Server 2003 another 1GB, too.
I'm doing it on my 64GB ram server ;) Hyper V + VSuite RamDsik