Hi .. (deep breath) I have a mid-2012 27" iMac with 3TB fusion drive. The REGULAR SDD failed, and apple replaced it. However, my computer feels slower than it used to, and I'm thinking that the "fusion" magic isn't happening. Is there any way to tell definitively if the fusion drive is working? I am getting low numbers on blackdisk speed test, but my 3tb drive is also 90% full ... so I want to know if there's a simple definite way to check if it's working? Thanks!!