It's not the same back up. If I have 20 new movies and it takes 15 minutes each to back up, it will take 5 hours to do 1 back up at a time using 1 drive as the writer and 1 drive as reader. However, doing 2 back ups at the same, while having the cpu to do it and 2 hard drives (physical hard drive) would take me 2,5 hours.
The problem is still the same, it looks like cloneDVD does not always detect new blank disk when it just "read" a disk but using a second drive as writer would help.
The real problem is that it only seems to do that with Verbatim DVD...so either I bought two 100 splinters with faulty dvds, either cloneDVD has a problem with those DVDs, in both case it is a shame since Verbatim are probably the best dvds (along with fujifilms) you can buy