Hi, I have a 2013 27" HD based iMac (Mavericks installed) and a 120GB external Samsung 840Evo SSD in an USB 3 enclosure and I'm wondering if it's worth combining them into a fusion drive. At present the hard drive reads and writes around 175mb/s. Are there any downsides besides one of the drives being external/vulnerable to disconnect? 1) Does this void warranty 2) Does this limit the life of drives? 3) Do time machine backups continue to work from an existing backup? 4) Would a DIY Fusion Drive create problems for future OS X updates? Thanks for any help!