Main Question : Would I see any benefit (I/O bandwidth-wise) to purchasing a separate (non-raid) PCI-e controller card to plug SATAII drives into vs on-board SATAII slots?
I'd be plugging at least four drives into whichever solution I go with.
For portability reasons, I'm running a fileserver in a VM (the physical machine is dedicated explicitly for running this VM), serving files from a number of virtual disks each located on its own physical hard-drive. The host has its own dedicated drive, and the VM is also on its own physical, software-raid-mirrored drive. Occasionally I'll see some slowdowns in the I/O for reading/writing files to/from the server and I'm suspecting the fact that right now all of this is being done over the PCI bus. (Limited to 100Mb/s vs 150Mb/s for SATA).
I was willing to tolerate being limited to 100Mb/s via the PCI bus, but I'm starting to want something faster.
The machine that is running all this is a little old (P4, no PCI-e slot) so I'm considering an upgrade. I'd like whatever solution I end up going with (just a new board with >4 SATAII connections or a new board and a PCI-e controller card with 4 SATAII connections) to have as much bandwidth as possible for the disks, without getting into enterprise-level controller cards etc.