[quote=@Sublimation]
Servants are just photo copies of the heroic spirit data in the throne of heroes. They dont retain any knowledge since they are separate things from the actual spirit. The only known exception is Arturia because of her pact with the world making it so that she hasnt technically died.
[/quote]

Actually not, there's a point on the VN where archer mentions that servants, thought perhaps  it was supposed to hint to his Counter Guardian nature, know what happened to them during a summoning just like they've read it from a history book. They're memories per se, but general knowledge of vents. Then again, like I said, perhaps this is just with Counter Guardians, 'cause that is the whole reason why he got so cynic after his death, Gaia kept fucking with him until he just gave up trying to be a hero.