[weblacky]

I'm using drives that are 70 plus gigs usually.

It takes forever even doing the sequential and I've never actually had it erase data. Maybe I'm not doing something right but yeah, how I would do it if I could fix the miniroot would be to have a /dev/zero type device that can just sequentially blast zeros and then mkfs.

I will say that I assume you know you can control where the exercise happens.  So you could read the section boundaries that the miniroot occupies and exercise the sequenced write in just that range.  As long you're not merging or hitting old data, you don't NEED to remove the disklabel.  Wiping the miniroot AND mkfs'ing the old XFS partition should be enough...I've just had miniroot issues without wiping...I think...never really looked into it once wiping worked.