I have a 2012 Mac Mini with a 500GB SSD in one drive slot and the stock 1TB HD in the second. Recently I found that the 1TB HD will get slow: -format drive it works fine for a while -drive benchmarks show it can read/write around 100mb/s -eventually I'll test again and the write speed is around 100mb/s, but read drops to 10-30mb/s -if left long enough it will get hung up on a big enough file that it just freezes the application. I use it for my EyeTV Archive. This means that when the drive gets slow ETV take a long time to open. It seems the video files recorded may also be less than perfect. Sometimes the audio is out of sync or the video freezes. I'm not sure if thats an issue from the drive or due to the antenna losing a good signal. I've reformatted the drive 3 times now. Each time it works and tests fine for a time. Usually just a week or so now before it gets slow. I've used Tech Tool Pro to scan for bad blocks. It does not find any, but it never finished either. After about 2 hours it gets so slow it would take 15+hours to finish. It seems the more the drive is used the slower it gets. Very odd. No sounds or other sings of bad blocks or a failing drive. Other drives (external WD duo, WD MyBook, and the system SSD) are all fine.