Datastore Filecaches slowes server down
 

When activating Datastore Filecache, my sites take around 3 percent more time to load. Why is that?I compared vbulletin Datastore Filecache with vbulletin running with no cache. Specification is as follow

Code:
Hosted Environment.
Guaranteed ressources: 1 Core, 2 GB RAM.
500.000 posts,
200 users online simultanously.
3% slower is measure by debug mode on FORUMHOME.