Excessive drive activity?

Ever since a reboot a few days ago (after I replaced the fan), the disks in my DroboFS have been churning pretty much non-stop. No shares are mounted and the activity light is not blinking, but I can hear the drives seeking/churning like mad, and over several days the Drobo has never idled. Top doesn’t show anything using CPU (everything aside from top itself is at 0.0%), and tools such as lsof don’t appear to be available for further diagnosis.

None of my DroboApps should be causing issues; at least, they weren’t last week. Here’s what I have installed:

Only thing that uses any appreciable resources is stgt, which is a bit of a memory pig, even when I’m not using iSCSI.

Any ideas?

I have replaced the fan for a year. At first I thought that hard drives work all the time. The truth is because the fan is quiet you hear the disks working. Many times DROBO shows no activity but activates the disks. I’m not sure for what reason perhaps to defrag and check data… I have replaced the fan with the noctua NF-P12 and my drobo is completely silent.
I use 2 x 2TB WD Caviar Green
1 X 640MB WD Caviar Green
Sorry for my English… they are terrible!!!

And just like that, it seems to have quieted down. Not a clue what it was doing the last few days, but I’ll be glad if it’s truly done.

After a day of this, I notice that while it’s quiet again it still doesn’t like to spin down. I really wish I could set the delay even shorter, e.g. 5 minutes.