My parents own a 27" late 2012 iMac which originally came with a Fusion Drive. However the hard drive failed recently and I have been left in charge of upgrading the 1TB hard drive with a 1TB SSD. I have everything required to perform the "open heart surgery". My parents are not very technical people and would prefer to see the drive as one, like they are used to, instead of two drives. So my question is whether it is possible to format the two drives as one and still enable TRIM on 10.10.4? The two drives are the 128GB SSD that the machine came with a 1TB Samsung EVO 850.