Do you think I need the VRDB to run or generate, it seems that my hard disk space becomes lower.
If you mean it takes up more space rather than slower, the VRDB doesn't make copies of files (it isn't like conventional backup), it makes information about the file to try and help repair it if it gets infected. It also doesn't do this for every file, commonly only for executables. So it shouldn't take up that much space.
If you do mean slower, I can't see how as it only runs when a) you manually generate it or b) every three weeks, which is its run interval.
If I generate a VRDB is there any option to remove the files used when generating?
No, because it isn't saving complete files as I mentioned above.