Do you have tapealerts turned on? If not, you should... If you do, take a look in your activity log for tapealert messages regarding corrupted LTO cartridge memory (do a "q act search=corrupted begint=now-08:00"). There is a known problem with IBM LTO drives that was causing the cartridge memory to get corrupted... when that happens, the file search performance is adversely affected. That's really an undrstatement... we recently had to restore a couple of windows servers C: drives. Took about a week (yes a whole week!) to restore 4GB. Granted, the data was spread over about 300 tapes, but I observed tapes being mounted for 30 minutes or more before any data was transferred.
The real bad news is that you first need to upgrade your drive firmware to prevet further corruption. Then, to rebuild the corrupted memory, you have to read all the data on each affected cartridge. One way to do that would be a "move data" command for each cartridge. Another way is to use tapeutil or some similar program to read through each tape. Either way, it's pretty disruptuve. And the only way you will know what cartridges are affected is by reading them and seeing the tapealert message.
I haven't even attempted to fix our tapes yet, because StorageTek is not yet releasing the latest LTO2 firmware.
Good Luck!
Robin Sharpe
Berlex Labs