Why does the Drobo slow down so much as you reach capacity?

So I have a DroboPro at work with 8x2TB in it that’s currently about 97% full. At this point the speed isn’t really a big deal, because this is just a backup of a Fujitsu Eternus 24TB video SAN (as opposed to using tapes), but at this capacity level things are copying over at about 1-2MB a second.

I understand that with RAID devices they get slower as they fill up, but our old Infrant/NetGear ReadyNAS devices were filled to 99% capacity in the past and never got to this level (slowness) in speed.

Is there a reason the Drobo slows down so much after 95%? Is it because the OS thinks there’s more space than there is and since the Drobo is tricking it, the only thing DRI can do is make it so unbearably slow copying data to it toward the end that it throttles is back like that? And if so, why is it 95%? 5% free on a 16TB volume is a lot of space. Why can’t it throttle back to 1K a second or something at 99.5%? And if a volume is 97-98% full, are the rebuild times also going to be absolutely horrid as well? Why was 95% selected as the throttle point?

yes there is a reason and its well documented.

once you get past 95% full the drobo DELIBERATELY throttles you to stop you from ever putting more data on there than it can physically hold. (its you have 16TB partition - and 12 TB of actual space - if you tried to put 13Tb on there you would have a problem)

and no, there is no way to change or override this.[hr]

there you go[hr]
ooh i see you’ve edited your post a bit.

well 5% increments were chosen back in the day with 1Tb disks - and a 4 slot drobo, so it didnt really matter so much.

yellow warning 85%

red warning and slowdown 95%

i dont think rebuild times will be affected by Drobo DELIBERATELY slowing down - but i wouldnt be surprised if it would appreciate a little free space to work with