Why is more data getting scrubbed than the pool is large?

[StephenFry]

I'd never noticed before, but on a pool that is 3.6TiB large and reports 2.7TiB free, with 879.9 GiB (24%) in use (numbers that seem to match, considering the rounding that happens), the scrub-in-progress tells me that 1.29T is getting scrubbed.

What's the math here? This is a newly created Z1 pool (3 x 2TB drives) that I copied about 900GB of data to.

 

[Stephens]

I don't know if this is your answer, but don't forget that it has to verify the parity information is readable as well.

 

[StephenFry]

I think the math on that adds up; how silly that I didn't think of that.