Didn't replace the smallest drive, what happens now?

Hi, I have five hard drives – 4 x 1TB and 1 x 500GB.

I bought a 2TB drive and replaced the wrong drive – I swapped out one of the 1TB drives.

I do have another 2TB drive that I plan to swap in for the 500TB later, though.

Now the Drobo is going through the relayout process with 3 x 1TB, 1 x 500GB and 1 x 2TB.

Will this still work or should I be worried?

It will still work but you won’t see any extra space because of how the redundancy works, you lose your biggest drive in single-disk redundancy and your biggest two drives in dual-disk redundancy.

Wait for the lights to go green then swap out the 500G drive. At that point you should see additional space. If you are in dual-disk redundancy then you will only see 500G, the two 2TB get used for protection. In single disk redundancy you would see 1.5TB extra.

The space calculator here: http://www.drobo.com/calculator/5-bay/index.php will tell you what you get in all combinations.