I'm having problems with the Drobo on the Mac Mini when I am rsyncing data to it.
The Mac Mini appears to be fine. There are four external hard disks attached to it, some through a powered hub. The Drobo is attached directly to the Mac Mini, not through a hub. I use rsync over ssh to duplicate my photos from my Linux box to the Mac Mini onto the Drobo. The script I use to do this is slightly modified from the scripts where I keep my music and my videos and my flacs all synced to the four external drives. I haven't had a problem with them before.
I start the sync process, and it chugs away nicely, transfers photos, puts them in the right place, everything going well, and then the Mac Mini goes grey screen and it's dead. The first time it happened, I restarted the Mac Mini and used Disk Utility on all my hard disks to repair the disks. All was well. A report came up showing that there was a problem which would be sent to Apple. It appeared to show a panic in launchd.
I started the Activity Monitor so I could see what was going on. Spotlight seemed to be working overtime. I guess that when you put a large amount of new data on the system, Spotlight has to index it. I waited for all activity to die down, no load on the CPU or memory, and started the sync process again.
It transferred a bunch of new photos to the new Drobo and then the Mac Mini did the grey screen thing again. I rebooted, ran Disk Utility and repaired all disks, and waited for all activity to cease. A second report about the failure got sent to Apple.
Then I did the sync again, but killed it every now and then so it wasn't doing too much. That worked for the rest of the night. I left it idle overnight.
Next morning, I started again. Not too far into the first sync of the day, it grey screened again. This time the Mac Mini did not come back so well. The top bar did not appear. The external disks did not appear. I think Finder was a bit messed up. Half an hour later, instead of right away, the report for Apple about the failure appeared. I couldn't do anything. By now, I was suspicious of so many USB connections with the external hard disks. I shut everything down, had to pull the plug on the Mac Mini as it would not shut down gracefully. I powered down all hard disks, totally removed all power, went and had breakfast. Then I came back and powered it all up. It all came up again and things worked properly.
I continue to sync the photos in small batches.
I suspect that there are too many hard disks attached for the USB to handle. Or Spotlight is causing me problems. Or the Mac Mini has memory issues. Or any of a bunch of things. I'll start with small things and work up.
First thing - turn off Spotlight. I do not use it. The Mac Mini is used solely for backup (Drobo) and as a media server to my Apple TV. I do not need Spotlight running. Google pointed to this page How To Turn Off Spotlight with the command
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist
and I did that and yes, it disabled Spotlight. I will keep syncing my photos and see if that makes a difference. If not, I will remove the other external hard disks and try again.
I have done long 3 T rysncs of data. But that was with the previous Mac Mini and these same external hard disks. The old Mac Mini was an earlier Intel Mac Mini with 2 gig RAM and it would rsync 3 T of data in one smooth continuous run with no panics or grey screens. The new Mac Mini has been in place about six months, and small amounts of rsync don't bother it, but it's never had to do a large sync like this before.
I'll keep testing and syncing.