Adding 6TB drives to DroboElite


We have a few DroboElite units and we are trying to replace some 2TB drives with 6TB.

Dashboard is 2.6.4, firmware is 2.0.6. Unit initially had 8 x 2TB drives, dual disk redundancy is enabled.

We pulled a 2TB drive from bay 1 and replaced it with a 6TB. The Drobo recognized the drive, but it didn’t indicate it was rebuilding, but the red light moved from bay 1 to bay 2. As we had dual disk redundancy, we pulled the second 2TB drive and replaced it with a 6TB as well. The red light has now moved back to the first 6TB drive, and it does not appear the Drobo is doing anything. When looking at the capacity line graph, it shows all the drives appropriately, but is not showing any extra usable space, just more space under ‘reserved for expansion’.

What to do now? We have 4 6TB drives (so 2 more), but don’t want to pull another as we’d lose data then.

Any help welcomed,



hi brian,
i would wait for longer, and if possible to also try rebooting them later on if nothing happens in the meantime,.

can you also check if those new drives are using the native 4k sectors? (i think only the emulated 4k drives are supported), just in case that is the reason.
also is probably good to Not try replacing any drives in a similar way on your other elite units for now.

if you happen to get a chance and can post some screenshots of data usage and drive status from dashboard, such as linking to imgur or similar, that could be handy too (but please rub out your serial number first to play safe).

Thanks Paul

Just got back from lunch, and it is rebuilding. Looking good so far. I’ll likely leave it for the weekend and do the other drives on Monday.

I’ll post an update then.



ok fingers crossed for you :slight_smile:

OK, it’s still rebuilding.

ETA was originally 1 hour (last Friday). Obviously we’re past that, it was saying 1 minute left yesterday, now there is no status or ETA?

Any suggestions? I’m leaving it be for the time being…

hi brian,
(the dashboard eta usually tends to be accurate near the start, but it can sometime be a bit like the windows progress bar when giving estimates, especially if something else uses the drobo a bit to slow it down etc)

if you can remember when it started to rebuild though, then it should usually take about 1 day, for each 1tb of data that you have on the drobo.

Just thought I’d put in an update.

Things finally rebuilt successfully. This particular stage of the rebuild finished on Dec 8, so over two weeks. We still had two more 6TB drives, but rebuilds only took 4-5 days (each drive) for the remaining drives.

Thanks for all the help,


many thanks for the info brian,
some factors such as a slower drive or rpms might impact a rebuild, or a struggling drive, as i think the rebuild process would be slowed down to the speed of the slowest drive, but am glad it all turned out fine for you :slight_smile:


Just to confirm, although Drobo’s site claims only 4TB drives are supported, you were able to access the capacity of 6TB drives on a DroboElite?

The reason that the first rebuild took so long was that you replaced two drives at once, the second set of parity calculations is far more intensive than the first , and it is having to recreate two drives worth of data rather than one