Drobo: one partition won't mount and nothing dismounts

[Robert Peirce]

Before Jolly Roger reminds that you aren't supposed to partition Drobos,
I have done this as long as I have had it and have never had a problem.
So, right or wrong, it works. Taking that as a given:

I have 12 partitions. The first 10 are for daily SD! backups of my MBP.
One is for occasional SD! backups on my Mini and the 12th, which is
about 12Tb is a Time Machine backup of my mini and the 4Tb drive on
which I keep my photos and music. I also have a 4Tb drive for Time
Machine backups on my MBP. I am pretty well covered for data recovery.

As of today something weird has occurred. When I go to mount the drobo
everything mounts but one backup partition. It happens to be the oldest
partition I recently used so it is the next one I would use for my MBP.
Option-boot sees it, although I didn't try to boot from it, and Disk
Utility sees it but I can't mount it or do first aid on it. First aid
just hangs. I can't erase it either. That hangs as well. It is like
the partition doesn't really exist.

On the other side, I cannot dismount anything, either individual
partitions or all. The only way to dismount them is to shut down the
computer and turn off the drobo.

All this happens whether the drobo is on the mini or the MBP I am not
getting any error messages from the drobo or either computer and all
five drives are green. The only thing new is I installed 10.13.2 the
other day. However, because I have to swap the drobo back and forth to
backup the MBP and mini, I know everything was working fine until this
morning.

I'm inclined to think something is wrong with the drobo but with no
error messages I can't imagine what it might be. There is also the
possibility of something happening with 10.13.2, but again, it was
working okay for several days.

I really need some ideas.

[Robert Peirce]

On 12/15/17 1:27 PM, Robert Peirce wrote:
> When I go to mount the drobo everything mounts but one backup partition.

I'll be darned. The partition finally mounted. It only took a couple
of hours. Now the question is why did it take so long?

[Robert Peirce]

Now that the recalcitrant partition has mounted I can now dismount
partitions. So, it seems, the entire problem had to do with the
reluctance of one partition to mount. Anybody care to guess why it took
so long?

[Chris Ridd]

Possibly the Mac was running a filesystem check on the partition, ie
fsck, perhaps because it detected inconsistencies.

That's the same thing disk utility does when it verifies a partition,
and it will take a long time if the partition's big. It will take longer
if there are fixes required.

If you unmount it (cleanly) and mount it again, it ought to mount fast
as the inconsistencies were fixed.

--
Chris