Drobo Migration from Drobo 2nd Gen to 5D

I’m in the process of moving off of my Drobo 2nd gen (4 bay, USB/FW 800) drive to a new 5D. New 5D is populated with new drives and I’ve manually copied all my content from the old drobo to the new one. iMac i5, Thunderbolt, etc. All is good.

Now, there’s 4 drives in the old Drobo that I want to repurpose. (3TB, 3Tb, 2Tb, 2 Tb). Ive taken one of the 3TB’s and moved it over to my 5N and it seemed to attach itself very quickly (no reformatting?). Drobo Dashboard (Mac) sees the drive and it thinks it’s good.

If I take the remaining drives and mount them on my Mac, the partition map is off and the 3TB Toshiba is seen as a 800GB volume. Using Disk Utility, Drive Genius, Disk Drill, etc do not have the ability to reset the Partition map correctly to get back the full storage map of the drive (to be seen as a 3TB volume instead of an 800GB volume).

Any suggestions on how to take a drive out of a drobo and reformat it so that I can make it a usable stand alone drive again?



Use the utility from the drive manufacturer to wipe/erase/write-zeroes the disk.
Most hardware disk clone hardware also have an erase or wipe option.

If there’s no Mac OS utility, you can also try using Gparted to erase the existing partition data.

Why do you think that Disk Utility can’t format the drive?

Did you erase and reformat as a GUID drive?

In verbose mode, what messages is Disk Utility reporting?


Thanks for the reply. The drive is a Toshiba DT01ACA300 (3TB) drive. If it’s placed back into a Drobo, Drobo Dashboard sees a 3TB disk.

Using Apple’s Disk Utility, It sees 3 “partitions” … All totaling to about 750GB (748.52 GB). Deleteing these and repartitioning the drive only goes back to the 750GB volume size that the tool sees. Other Mac Based tools (Drive Genius, Disk Warrior) also sees this drive as considerably less than what either came out of the box or what the Drobo (5D/5N) sees it as.

I did try GParted – and the same behavior is seen – it only sees the drive as a 750GB unit.

I’m suspecting that something is affecting the drive at a deeper layer. When the bare new factory drive is inserted into the Drobo unit, I’m assuming (now) that there is some very low level things that go on with the drive, or possibly the drive firmware so that when the drive is removed from a Drobo pack and expected to stand on it’s own as a repurposed bare drive, it retains the low level config data that Drobo tweaked and shows itself as using this new low level map data to other host systems (Mac, Win, Linux, etc).

So, I’m guessing that I will either need to get help from Drobo (officially) or from Toshiba to get the low level drive data back to “Factory standards”.

In my research, I’m coming across the issue of large platter drives having 4K sector sizes, and from what I can see in GParted, it looks like they are mapping the sectors to 512Mb (an 8x loss in calculated size). So the sector count still may be accurate, but given the 512mb / sector mapping size, it calculates down to 750Gb (I haven’t done the complete math on paper, just off the top of my head).

So, any advice on how to get a large capacity drive to get back to 4K sector sizes from 512mb?

TIA … (off to do more research and to call Drobo support).


@MGRIFFIN – I took the drive out of the Drobo, put it into an external SATA chassis (USB 2.0) connected it to the Mac and Disk utility SEES the drive, but it only sees the drive as a 750g unit (instead of the 3Tb unit it has seen before using a non-Drobo’ed Toshiba drive).

Doesn’t matter if I connect it to a Mac, Win 7, or Linux (GParted Boot ISO), they all see the same thing. I’m suspecting that part of the Drobo preparation process for a new drive is to do some low level magic to the drive tables - the same drive put back into the drobo pack is seen as a 3TB unit.

Check the comments to Brandon above and see if what I’m seeing makes sense.

Thanks for chipping in, let me know your thoughts.


I don’t think Drobo makes any firmware-level changes to drives (nor do I believe it has the “smarts” to do so).
It might be using an altered partition structure (GPT/MBR), but much of it is black magic to us as end-users. :slight_smile:

Hmm… I see mainly older disk utilities on Toshiba’s page

Since the system sees the drive, regardless of its oddballity, you can try Darik’s Boot and Nuke (DBAN)
but do NOT use autonuke and be VERY CAREFUL otherwise it will nuke your system drive too!!
If you have a spare computer, highly recommend using that.
If not, disconnect your system drive if you can.
If you have any hesitation, ask a trusted tech-savvy friend to do it for you.

It might? work to…
Shut down Drobo
Remove all drives from Drobo
Insert only the problem drive
Let Drobo boot
Do a pin reset
Wait for reset to complete
Shut down Drobo

No, no “low-level magic” involved. Modern hard drives (like no older than a decade (or two?)) don’t allow connected host to perform any low level format style operations anymore. Also, Drobo definitely doesn’t mess with drives’ firmware. I don’t think your theory regarding 4kB sectors is true, either. As far as I know, we’re still in the “512e” transitional phase of the “Advanced Format” where HDDs use 4kB-sized physical sectors internally but make this fact transparent to the host and present (and work) as 512kB-sectored devices (http://en.wikipedia.org/wiki/Advanced_Format#512e )

Like advised, just use the tool provided by the drive vendor to zero the drive out. It could take many hours to clear the whole drive but you should be fine after just a few minutes of erasing.

hi, while reading i was going to suggest looking at dban as well.

one thing which i’d be interested to know (if a chance ever arises) is this…

  • does a fresh brand new toshiba drive of the same make and model etc get detected at its true 3tb capacity if connected to a computer first?
  • if so, does the same 750gb representation still happen on that new drive, after being used in a drobo?