Here's the situation...my nMP has a 1TB internal SSD. With the OS, programs, documents and VMs it has about 550GB used. My Drobo 5D (connect via TB) has my iTunes, iPhoto and iMovie libraries. For whatever reason the Drobo will put the disks to sleep if not being used. Every time I listen to music or switch over to iPhoto I can hear the drives spool up and it takes 8-10 seconds. Also sometimes when I fast forward from song to song in the library the response time is a bit slow. The lag is driving me nuts. A long time ago I heard that when a drive gets over a certain percentage full it's performance is degraded. I wondering if I move at least my iPhoto and iTunes libraries back to the internal SSD (to get rid of the lag), increasing the usage from 550GB to just over 900GB, whether I'm reaching that point? BTW, what is the point where performance suffers...90%, 95%, 99%?