disappearing free space

I saw one other mention of this from a couple of years ago, but the issue wasn’t resolved.

I have a Drobo S (I think 1st Gen). Yesterday I noticed two things:

  1. I had a drive failure
  2. Where I should have had 1.5 TB free I now had exactly 0 bytes free.

I’m on a Mac, and I know I have to be careful to not exceed my capacity.

I immediately deleted 50 GB of stuff and ordered a new drive.

I came back later that night and only had 25 GB free. By the time I called support (unsuccessfully…I’m out of warranty), I had 20 GB free.

I’m not good at reading iotop, but I find nothing of consequence writing large amounts of data. Also, I du’ed the root directory of the volume, including invisible files, and nothing is changing size.

My only hope/theory is that the drive failure caused the Drobo (which had 2-disk redundancy and now has 1) is shifting data around to reprotect, and it is just screwing up. I’m hoping that when I get the new drive, the problem will resolve itself.

Barring that, I don’t see what else to do apart from investing in an entirely new system.

Any tips?

Edit: Under Drobo Dashboard, the space “Used for protection” is increasing. That’s where the space is disappearing to.