My rule of thumb for a physical server was fast random access disk (VelociRaptor/SSD) for OS, and large disks for data (e.g. WD Caviar).
How does that look for a Hyper-V that should run two virtual machines (File Server+Intranet, Dynamics CRM)?
- Does it still make sense to put the physical OS on a separate disk?
- How much disk space / RAM should I set apart of the physical OS?
- File Server: Is there a notable difference of a pass-through disk vs. VHD? Any preference for one or the other regarding backup, Volume Shadow Copy Service, other stuff?
- Should I split the virtual OS parts (FileServer-OS, FileServer-Data, CRM) onto separate physical disks? Say, with mirror 2x2x1TB, or 2x2TB?
- How do you backup a 'life' VHD? "as usual" from within the server?
I've read the related questions and the system requirements stated by microsft, I am more looking for practical input, from people who've done it before.
 The specs are still open, I am aiming at an i7-920 quad core, board e.g. Gigabyte EX58-UD5 (open to suggestions) 8GB RAM
I am aiming at a total disk storage of about 2TB.
Idea 1: 80GB SSD for Hyper-V, 2 x 2TB WD RE4-GP in mirror for the two VM's, totals at about €850
Idea 2: 4x1TB WD RE-GP in 2 mirrors, resulting in 2x1TB storage, one pair for HyperV and first machine, the other for the second one. Totals at €520, would allow another 4GB of RAM that might make a huge difference.
 A commenter asked for the final configuration, here's what I learnt (and what we did)
I decided against a hardware raid, due to bad experiences with various controllers, the low overhead of a software mirror, and the simplicity of transfer to another machine.
We put the most busy network share on pass through disks. They are "offline" in the HV host, and mirrored in the virtual machine. Performance is adequate for our purposes.
I did add a separate OS disk, simply to be more flexible about the configuraiton. (WD Raptor 300GB).
So we have configured one pair of 1TB as pass-through, the other pair is mirrored in the HV host and holds the VHD's for both servers.
Note that passthrough disks disable snapshots in Hyper-V-Console (I wish there was an option to just exclude them but proceed with the snapshot). I also learnt the hard way that snapshots were a bad idea anyway since it breaks active directory sync.
Backup is to an external disk attached to the host through e-sata.