I received a notification that one of my drobo drives were in need of replacement. I replaced it following the directions of just putting the new drive in and letting data protection run. It’s been running for over 24 hours. Every now and then I get a message that I need to format the volume. I click “No” because it’s unclear as wo whether I am formatting the disk in the new bay, or the full Drobo drive where I’ll lose EVERYTHING, which is what I do not want to do.
It looks like your new drive is attempting to create a new, separate volume. It does not appear to be adding to an existing volume. If you allow it to perform the format, you will have two separately addressable volumes on your Drobo (ex: an E: drive and an F: drive).
I notice your volumes are sized at 16TB, which is quite small. This is likely due to the fact that your Drobo is either at a firmware version prior to 3.5.0, where 64TB volumes were enabled, or that the volume was created prior to your Drobo receiving the upgrade to version 3.5.0 (larger volume sizes are only possible on a fresh install, not for upgraded volumes).
To get out of this situation, you would need to back up all your data to someplace off your Drobo. Then, you would need to make sure your firmware is at the latest version. Finally, reset your Drobo so you can create a volume at the latest firmware version, which will be sized at 64TB, and restore your data to Drobo.
Edit: or, you can create multiple 16TB volumes and store your data on these multiple volumes (if you don’t want to hassle with moving then restoring your data).
I hope that helps!