gdh
Looks like you have made a RAID1 array out of the 3 disks, sda, sdb & sdc (2 + spare).
That happens when you connect the 3 disks inside the server & then do an install from CD media.
The installer sees the 3 drives & automatically decides to create a RAID1 array.
That is normal behaviour.
That's also why you get drive busy errors when you sperately try to mount the drives.
OK, you need to disconnect the 2 physical drives (1Tb & 4Tb), then reinstall from CD to the 40Gb SSD (with no other drives connected).
Then after 1st boot & configuration, shut down the server & physically reconnect the 1Tb drive.
You should zero out the MBR on any already used drive, so be sure to do that see,
http://wiki.contribs.org/Raid#Reusing_Hard_DrivesThen follow the Howto steps & get it all working with one additional drive.
When all good, shutdown the server & connect the 4Tb drive & follow the same procedure (using GPT).
Remember you will have this same issue if you do full version upgrades in future, so you have to disconnect extra drives before installing from media.