I have Asus P6T Deluxe V2 motherboard with integrated HDD controller providing 6 SATA II (3 Gb/s) ports. I use this controller for 2 SSDs and 4 HDDs. SSDs and one HDD are for host system (Windows 7 Ultimate x64). Remaining hard drives store virtual machines (VirtualBox).
I sometimes need to run multiple virtual machines to simulate some environment. I noticed that "speed" of those machines drops if I run multiple of them in the same time (they still have same amount of RAM and CPU cores assigned) and I also noticed heavy disk usage. I understand that this can happen if I run two machines from the same drive but it looks like machines running from different drives somehow share the throughput as well. Is my suspicion correct or should I look for problem elsewhere?
I wonder what benefits will be to use some separate specialized HDD controller - for example some Adaptec device like 6405E. I don't necessarily need RAID at the moment but it can be useful option for future - I think I'm looking for increasing performance and throughput of separate drives.
I also don't understand controller's features. What does port mean? Some devices offer 4, 8 or more ports but also mentions expanders to connect tens or hundreds of HDDs. Does it mean that port is single dedicated bus which can be shared (bandwith can be shared) among multiple HDDs (in case of expander)? How many these dedicated "ports" are available in integrated controllers?
The mentioned controller offers 6 Gb/s ports. Does it mean that I will be able to use full speed of SATA III drives?
The separate controller is quite expensive device. Will it improve my experience (performance, data throughput) in mentioned scenario? Will it improve my day to day experience with my computer used for everything from browsing Internet to play games or develop applications? In short - does it worth to invest into such device if the mentioned scenario is not the main usage of my computer?