I run Proxmox 2.0, and installed Windows 2003 R2 (32-bit) server on it. I've use VIRTIO disk and NIC virtual devices (and installed appropriate drivers into Windows), and everything's fine. Physical server is HP DL 180 G6 with RAID 410i (256 Mb battery-backed cache, 4 x 300 Gb 15K SAS disks in RAID10). Server is UPS-backed (of course) so it won't suddenly be poweroff.
Now I see I can set disk mode in Proxmox to 'default (no cache)', 'Direct sync', 'Write through', 'Write back', 'Write back (unsafe)', and I can also on/off cache mode in Windows iеself. I'd like to optimize Windows Server IO speed, so I'd like to use 'write back'-ed disks, while at the same time it looks like I don't need Windows cache on disks at all.
What's the better strategy for my case? What mode I need to set for virtual disks in Proxmox, and what setting are better to use inside Windows Server in VM?
By the way, what if I install Debian in another VM on the same Proxmox - what disks modes should I set in Proxmox for better IO performance of Debian?