The issue you are running into is with ESXi and its use with BUE and the tape drive. Here is a link that has some info that should answer the questions you are having. kb.vmware.com/.../search.do 
Hello all We have recently spent a few thousand pound purchasing a POWERVAULT 114X with one LTO-6 drive in it. I have a Dell server running VMWare ESXi. I have configured VMWare (Pass through) and the SAS HBA is visible and installed on my Windows 2008 R2 server. All seems well, except that I cannot actually see the tape drive. I have installed Backup Exec 2012 on the server and it does not detect the drive. I have looked everywhere for a Windows driver for the tape or any software needed, but I cannot find anything anywhere (apart from some firmware updates), no documentation at all. nothing. Clearly I am missing something. Can anyone advise please? I am going bald from scratching my head figuring this out.  Regards  Calvin
Installing and using POWERVAULT 114X on Windows