error event 11

I have a drobo s connected to my windows home server 2011. Recently I have had 2 episodes where I started having problems with the connection to my drobo. Looking in the log I got an event 11 errror which is a hard drive controller error. Restarting the drobo fixes the problem. What I am trying to figure out is this a drobo issue or an issue with my usb controller or something else?

Any suggestions?

hi can i check which cable you are using to connect it to the computer, (and if its going through any convertors or hubs etc?)

also, was there a large period of inactivity (such as power saving or screensaver mode near those issues?)