Drobo is running wild

I’m having an issue with my first gen Drobo. All of the sudden it started making all kinds of data read noises. The hard drives sound like they are moving data like crazy. It has been doing this for days now and I can’t seem to figure out why it’s doing this.
I use the drobo to rip music to and I can’t even rip a CD to it from iTunes without it taking hours now. It used to take 5 minutes.

Here is some info on it:
1.5 TB WD Caviar Green
750 GB WD Caviar Green
750 GB WD Caviar Green
1.0 TB WD Caviar Green

Used: 1.99 TB
Free: 274.78 GB
Total: 2.26 TB
Mac OSX 10.5.8
Drobo Dashboard: 1.5.1 [1.5.19930]
Drobo Firmware: [1.252.21110]

I know I’m running a little low on space but I can’t imagine that it would cause this issue. Does anyone else have this problem or can maybe shed some light on this? It’s driving me bananas.
Thank you in advance!

The drobo does start to slow down a little at 85% full. Usually you cannot tell or see the slow down until 95% full.

I would recommend a repair disk from disk utility or chkdsk from command prompt depending on your OS.