External HD keeps disappearing from desktop

[jm102030]

Ok, so I bought a new iMac 27" 5k this week and a LaCie 2Big 6TB RAID to go along with it. So far everything's good. However, I noticed that the LaCie HD disappears whenever I shut down the computer and turn it back on. The HD goes to sleep when I turn off the computer (blue light goes off) and it powers up again as soon as I turn on the computer but then it doesn't show on either the desktop or the "devices" panel in finder. When I then turn the HD off and on again it appears on the desktop. Right now the HD is still empty and I formatted it as "Mac Extended Journaled" (no encryption). It's attached via the Thunderbolt 2 port.
What could be the problem?

 

[jm102030]

I forgot to add: It does still show in Disk Utility and it only happens when I shut the iMac off, not when I put it in standby

 

[nambuccaheadsau]

Go into Finder Preferences and make sure 'Ext,ernal Disks' is selected.

I trust you do eject the drive correctly when you do get it on the desktop by using right click 'Eject' or dragging to ntheTrash.

 

[jm102030]

Go into Finder Preferences and make sure 'Ext,ernal Disks' is selected.

I trust you do eject the drive correctly when you do get it on the desktop by using right click 'Eject' or dragging to ntheTrash.

Oh, I should've mentioned, that was the one thing that I already tried. External Disks is selected in the Finder preferences.

I do eject the disk properly when I unplug it or anything like that but not when I just power off the iMac and leave everything connected. Surely that's not necessary, right? I've never had to do that on any computer.

 

[nambuccaheadsau]

If you power off your Mac I would eject, particularly if it is bus powered.

 

[jm102030]

If you power off your Mac I would eject, particularly if it is bus powered.

It's not bus powered, though. It's a RAID with two 3TB drives and I have set it to RAID 1 (in case that matters). I've never had this problem with any of my regular cheap external drives on my PC unless they were old and failing. However, I don't think in this case anything is broken because the "issue" can be perfectly recreated every time. I think maybe it has something to do with using thunderbolt. I guess I'll try USB3 and see if the problem is still there.