[UPDATE – June 2013]
I’ve just encountered the same issue using Windows Server 2012, System Center Data Protection Manager 2012 SP1 and an Overland REO 4600 VTL. As with DPM 2007, the fix is to change the tape drive driver to the generic Microsoft LTO tape driver.
I’ve used System Center Data Protection Manager (DPM) since the 2007 beta, primarily for SharePoint and SQL backups. I have a primary DPM server which backs up to disk and a secondary server which backs up to disk and additionally to a Overland Storage REO 4500 iSCSI Virtual Tape Library (VTL) for long term protection. Both servers have run Windows Server 2008 R2 with DPM 2010 since its release.
I’ve never had any major issues with DPM until I recently rebuilt the secondary server from scratch with a clean OS install of Windows Server 2008 R2 SP1 and DPM 2010. What I found was that although DPM installed correctly it couldn’t see the tape drives in the VTL. All the tape drives and the medium changer were visible in Device Manager and none were showing errors. The medium changer and driver were automatically installed by Windows and the tape drive driver came from Windows Update. The REO 4500 emulates an HP LTO2 tape drive and this is what was displayed in Device Manager.
In the DPM console under Management -> Libraries, the library was listed, but Total Drives was 0, rather than the expected 16. The DPM console showed the following error:
Tape Library Overland Neo Series Medium Changers is not functioning efficiently for the following reason:
The drive information for Tape Library Overland Neo Series Medium Changers is incorrect and needs to be refreshed. (ID: 3302)
I followed the instructions to remap the drives here: http://technet.microsoft.com/en-us/library/bb795782.aspx. The DPMLA.xml file produced by the tool was correct, showing the correct SCSI IDs, serial numbers etc. but DPM still couldn’t see the drives.
I found the solution to the problem on the DPM forum here: http://social.technet.microsoft.com/Forums/en-US/dpmtapebackuprecovery/thread/1d599443-7bf6-437a-bf12-52847fa7c8e5/ What I did is update the tape drive driver to the Inbox LTO driver as described on the forum and below:
1) Open device manager
2) Locate the tape drive
3) Right-click and look at the properties.
3) Under the DRIVER tab, select UPDATE DRIVER
a) Select the Install from list or specific location (Advanvced) – next.
b) Select Don’t search. I will choose the driver to install. – next.
c) Uncheck the Show comtabile hardware checkbox.
d) Highlight LTO under the manufacturer.
e) Highlight the LTO tape drive under model – then next.
f) This should install the Microsoft ltotape.sys driver.
4) Rescan the tape library in the DPM console – try to take another backup.
After following the above steps, all 16 tape drives were visible in the DPM console.