If you bought an iMac in May and July this year and chose a SSD drive 1 TB HD from Seagate as a way to store, we have good news and bad news. The bad news is that your computer may be in the "small number of iMacs" that showed a defect in this drive.
The good news is that Apple is already providing the recall. Just put the serial of your iMac here to see if he was affected or not and provide the exchange of the drive.