Some Seagate Barracuda drives have been found to have buggy firmware which causes the drve to hang or become unresponsive after a power-cycle event (such as the computer going to sleep or standby) and the drive need a full power-cycle (power off then back on) event to become operable again.
Please note that you may not experience this issue when running the drive with the latest drivers in Windows, but may experience it in Linux-based OSes, such as Ubuntu Linux. This is because the issue is covered up by Windows drivers. If you experience the issue in Linux, then you likely have a drive with faulty firmware. Note that this is supplied from Seagate to Dell, so the fault lies in the firmware developed by Seagate, not by Dell.