Saturated VRAM vs system RAM

If I allocate more VRAM than the one prov?ded by my AGP video card, it swaps on
system ram. The questions are:
1)are HWSURFACEs swapped to system RAM slower to SWSURFACEs? Is this hardware
dependent?
2)How can I make sure that certain surfaces are always kept to VRAM? Should I move
surfaces manually from VRAM to
sys RAM in order to never get the VRAM swapping?