Replace and add drive

Recently, a drive on my drobo crashed. The drobo switched back to three drives, and is now back to normal (with data protection).

I bought two new 2TB drives. In what order should I upgrade?

  1. Replace drive 3 with new one.
  2. Wait to rebuild.
  3. Add drive in bay 4.
  4. Wait to rebuild.


  1. Add drive in bay 4.
  2. Wait to rebuild.
  3. Replace drive in 3 with new one.
  4. Wait to rebuild.

Furthermore, is it necessary to wait for the rebuild, or shall I just replace and add drive at the same time?


Replace the drive in bay 3 and add the new one in bay 4. You can add drives while drobo is rebuilding, thats no problem. There is no need to wait until drobo finished rebuilding after replacing the drive in bay 3.

you can replace an add at the same time, although it may make the overall process take longer.

essentially there is no practical difference between your two methods.

the first way - when you ADD a drive there is no step 4 - no wait to rebuild, if you are adding a drive, ist instantly available and that is it (drobo may do some processes in the background - but you cant tell)

the second way - again when you ADD a drive - there is no step 2/wait to rebuild

STOP! After adding a drive into bay 4 he has to wait until the rebuild finished before he can replace the drive in bay 3!

Thanks for your quick replies, I’ll replace the drive in bay 3 and wait for the rebuilding process to finish. I’ll add the fourth after that.


no, not at all!!!

if you ADD a drive - drobo DOES NOT rebuild.


what is it “RE-building”??? - there is no MISSING data for it to re-create

if you have 3 solid green lights and ADD a 4th drive - you will (within about 5 seconds) go to FOUR SOLIDgreen lights.

yes, drobo will re-layout in the background (i.e. it doesnt tell you it is doing it) and it is still fully redundantly protected and has FOUR SOLID GREEN LIGHTS

a background re-layout/optimisation (since that is what it really is) is very very different to a rebuild.

Ignore RFZ

Okay, so I add the fourth, then drobo starts creating parity over 4 drives (in the background). And then during that (lights are all showing green), i’ll remove the 3rd drive and directly add a new one?


as long as all the lights are solid green you can remove the other disk.[hr]
once you add the fourth drive - who knows what drobo does

maybe it does relayout the data in the background, maybe it waits until you actually write to the device before starting to utilise the additional capacity

the point is it doesn’t matter, there is no re-build (by definition!) since you are ADDING capacity not taking it away - there is nothing which needs re-creating :slight_smile:

RFZ’s thinking is very out of date and is too much along the lines of old legacy RAID arrays, which is not how beyond raid works/is designed to be used.

Well if there is no rebuild, then there won’t be a problem to wait until it finished :wink:
You know that I often replaced or added drives to my Drobo. In general, you’re right, drobo will not do relayouts after adding a drive.
But I’ve seen my lights flash sometimes after adding a drive to my drobo which has been in a stable state. Sometimes only for a few seconds, sometimes for a couple of minutes.

There is nothing wrong with my suggestion to wait until rebuild finished. If there is no rebuild, fine, go ahead.

Edit: My thinking is not related to old raid systems, I never used one… It’s just my experience with my own drobo.

Anyway, I’ve added the fourth drive, then when all lights were green I took out the third and replaced it.
All lights burned red for about a minute or two, but it’s happily rebuilding now and it lets me access it’s data.


try and avoid using it while its rebuilding as this will slow it down (its perfectly ok to use it - but ideally you would want to get back to a safe state as soon as possible)

Generate a diagnostic file and send it to DRI after rebuild finished. I won’t accept such a behavior…

So, about an hour ago the drobo indicated another drive had failed. (Bay 3, one of the new drives). Personally: I don’t trust it. The software told me to get it out, so I took the disk out. At that point, drobo got all red and told me I had removed too many hard drives. I rebooted the drobo for a couple of times with the 3 and the 4 drives in it.

It took four to five times, but it’s now rebuilding again (over 3 drives), my data is still there…

When it’s completely done rebuilding, I’ll try to add the fourth drive (which drobo marked as bad) again. I believe there’s nothing wrong with it… The last drive my drobo marked as failed (3 days ago) is still happily running in another enclosure and has written hundreds of gigabytes since…

It tends to mark them as failed when they are dying rather than totally dead

It could be taking too long to respond, an undue increase in number. Of bad sectors, all sorts, drobo is overly cautious… But i would trust a drive it has failed…[hr]
You can send dri your logs and they will tell you why drobo failed the drive, i would wait to hear that before reinserting it

Good idea, how do I that? Open a support case and use the drobo dashboard to ‘get diagnostic info’?

Thanks for your help again guys :slight_smile:

Yes, but get diagnostic AFTER the rebuild has finished (it can cause it to restart otherwise)

Understood :slight_smile:

I’m RMA’ing the new 2TB drive that Drobo marked as failed. I tried the drive again today, causing the HD in the 4th bay to come loose. I tapped it lightly so it made contact again, but Drobo already started rebuilding. So now we’re rebuilding again… joy! Happened to a friend of mine too, so lesson learned: Disconnect power from drobo before doing anything physically to the unit, there are some ‘loose contacts’.

I’ll be opening a support case and sending diagnostics info to see why my hard drive failed. The hard drive seems to work fine in another enclosure, so I wonder what Samsung is going to say about it…

It’s good advice that Docchris often recommends. :slight_smile:

I’m curious as well, especially as I’ve never dealt with Samsung support before.

I’ll let you know what Samsung says. I’ll probably ship the drive to them tomorrow, haven’t had the time yet.
I’ve also just opened a Drobo support case. Wonder why my drobo marked the drive as bad…