Why does CCleaner only take 1hr to free wipe ~400GB?

[loveranger]

I used both Eraser and CCleaner to wipe my laptop hard drive with the same file erasure method. How come CCleaner takes only an hour, whereas Eraser takes upto 5-9 hrs using the same 1-pass (pseudorandrom) method with cluster tips enabled? What is Eraser doing that CCleaner isn't doing?

 

[Joel]

Erasing cluster tips. Erasing cluster tips cannot be measured by the amount of bytes erased since opening and closing a file takes a significantly longer time than just writing continuous data (on a hard disk, anyway; SSDs are a different story)