What is the verification?

[dolphin]

Hi~
I'm trying to test the 'dban'.
During test, I found a different between verification on and off mode.
In my testing, the verification on mode is longer twice than off mode.
I would like to know verification's roles. in detail.
if it is effect before or after overwriting.
and why the amount of time is different.

I'd appriciate it if you give me the answer.
Thank you..**

 

[dajhorn]

Verification mode reads back each pass of the wipe and compares it to what was written. Each difference is an error.

Runtime usually doubles because most disks read data at approximately the same speed as they write data.