DroboPro not letting me replace failed drive

I’ve been having a rough few months trying to get my Drobo Pro working properly again. It has 8 drive bays, and almost 11TB of space used up. I have dual disk redundancy set up. A couple of months ago, it gave me a yellow warning that I needed to add more space. I had had eight 2TB drives in this thing for years. So I put in a new 4TB drive where there was a red light indicating drive failure. After weeks of data protection yellow and green lights flashing, there was yet another red light and another drive to replace. Luckily I had four 4TB drives at my disposal. After I added this second 4TB drive, it did the same thing–data protection, and now another drive needs replacing.

Now, I’d be fine replacing each and every drive and waiting months through all the data protection cycles–no problem–but now that I’ve gotten to the 3rd dead drive, it won’t accept a new drive. When I pull it out, the whole thing shuts off, restarts and then says I’ve taken out too many drives. I did a slot flush cos nothing I do has any effect apparently, and it looks like two of the original 2TB drives are dead, including the one I’m trying to replace right now. I figure if I do finally get this to take I’ll have to replace the other one too, which is fine. But why is this happening? Has anyone come across this problem before? Anybody have an idea as where I can go with trouble shooting this issue?

So for the record that’s 2TB + 2TB + 2TB + 2TB + 2TB + 4TB + 4TB + 2TB = 20TB

Thanks in advance for any help!

Keep in mind Solid red light means the unit is close to being full. Blinking Red light means the drive is bad. Also, Drobo uses the largest size drive for redundancy. If you only have one 4TB drive and the rest are 2TB this does not buy you anything. If dual disk redundancy is enabled this could also be a factor. Last, be sure not to add drives while the bay lights are flashing Amber/Green.

When you say that a drive has a red light, do you mean a steady red or a flashing red? They mean quite different things. Flashing red indicates that the drive has failed. Steady red is an indication that you should replace the drive with a larger one. When you replaced the first 2 TB drive with a 4 TB one you didn’t actually increase the capacity available for storage because, being the new largest drive in the array, there is nothing to protect the extra 2 TB, so that space remains reserved for expansion. Since you have dual disk redundancy enabled, replacing the second 2 TB drive with a 4 TB similarly didn’t increase the available capacity. This is explained by the fact that dual disk redundancy requires two of the larger size drives to protect the extra capacity of a third. So, once you have successfully replaced the third 2 TB with a 4 TB you will see an increase in capacity. To see this visually have a play with the Capacity Calculator. As a rule of thumb, add together the capacities of all your drives and then subtract from the total either the capacity of your largest drive (if you are using single disk redundancy) or the capacities of your two largest drives (if you are using dual disk redundancy). There are other overheads, but that calculation will get you in the right ball-park.

You replaced two drives successfully but on the third it rebooted. That’s annoying. If you’ve read threads like this or this and still haven’t fixed it then I don’t have any further suggestions as I’m not familiar with the eight-bay Drobos. Someone else might be able to help though. Have you contacted Drobo support?[hr]
Ah! DroboMod posted while I was composing my reply.

Thanks! I did not know that about the solid red light only indicating low on space, not failure. But I did do the slot flush, as mentioned in my post, and while doing so I was told by Drobo Dashboard that two of the old 2TB drives are, in fact, dead. It reads them as nonexistent. One of which is the one that is currently being indicated by the solid red light. I wonder if the fact that there are 2 drives not being properly read by Drobo is the cause of this reluctance to allow me to remove one of them.

I am aware that adding the two 4TB drives has not increased capacity, which is why I’m anxious to have this third one in there! I’m just trying to figure out if there is anything else I can do? I know Drobos are really finicky and I’ve been able to sort out problems in the past simply by trying different things over and over in different ways but now I’m at a loss. No matter what I do, the Drobo shuts off and says ‘too many drives removed’ when I simply try and replace the drive it wants me to replace.

Sounds like you have a drive that failed during the data protection mode. Would you create a case and submit a diag. then direct message me the case number.