It seems that (but I'm not completely sure), that when I'm copying files from gigabit network to HDD, I can't use full potential of the network which in my case is about 60 MB/s, because HDD writing is so slow like lower than 10 MB/s, and also it's slowing down the whole system which becomes pretty much unresponsive, almost impossible to work with.
Copying files to samba share residing at Ubuntu machine, connected to share from Windows 7, I'm completely sure my network equipment is OK, and there's no CPU intensive process on Ubuntu except smbd getting about 10-20% from time to time which I think is OK. Something here is burried deep I think, maybe even in kernel.
Already tried to switch from AHCI to compatibility mode, and turning acpi on and off - nothing helped. So it's like HDD buffer is full and emptying slowly while machine is sluggish, load is about 3 to 4.
Somebody experienced the similar problems? Some help on troubleshooting process and identifying the cause would be helpful too :)