Constant Disk Activity


My Gen3 DAS unit is running the most recent firmware (3.0.1 [89480]) under the most recent Mac OS X (10.12.4), and the disks have been thrashing constantly for weeks. All systems report green under Drobo Dashboard. Disk Drive Spindown is checked. Activity monitor shows a quiescent system (very low CPU load), yet the disks continue to thrash as if terabytes of data was being accessed. I don’t use it for backups, so there should be no other system access happening. The constant disk activity even continues when the unit is dismounted. Any ideas why this is happening, or how to fix it?


hi can i check what happens if the drobo is running normally, and then the mac is shutdown?
does the drobo then go into standby mode?

it could be part of the data scrubbing / verification process, that periodically takes place, (or part of the space reclamation process if you just recently deleted a lot of data/files), but either way, it should not take longer than about 1 day per 1TB data that you have in your drobo, just based on my own experience recently on a drobo-s-gen2


Hi Paul. Yes, the Drobo goes into standby mode as it should. But after the next restart, the disks start thrashing again.

I finally broke down and backed up the 2 TB of data on the Drobo, did a “Drobo reset,” reformatted the Drobo drives using Drobo Dashboard, and restored all the data back again. After optimizing the data overnight, it now seems to behave normally. The thrashing has stopped.

Since everything is back to normal, this leads me to believe that third party tools are the culprit. Before the thrashing problem started, the Drobo was failing to mount when the Mac was booted (this started shortly after upgrading to Sierra 10.12.4). So I used Apple Disk Utility to repair the Drobo. When that failed, I used Disk Warrior, as recommended by Drobo. That fixed the mounting problem, but somewhere along the way, the thrashing started. While resetting the Drobo ultimately fixed the thrashing problem, I’m now concerned that the current versions of utility programs are incompatible with the native Drobo HFS+ “format,” and there is no good way to repair the Drobo filesystem without introducing other issues, like the thrashing. I suggest that Drobo look into recent changes introduced in these third party tools for compatibility.


thanks for the update,
its good that things are working ok, at least currently…

(would you be able to keep an eye on things to see if in a months time, the scrubbing takes place? i think it was once a month if i remember what docchris said and and just wondering what happens in a month)


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