>It's more hardware than software problem, but I think it's the best place
>to ask.
>What are the advantages of using dual gripper instead of single one?
>Did You observe any improvement in library's performance? Currently we have
>few 'traffic jams' during the day and are thinking about changing our single
>gripper to dual one. But I'm not sure will it help solve our performance
>problems :(

To ask such a question, you must not have children.  :-)
When things get busy in the household called the tape library, the accessor
saves travel by being able to pick up two nearby tapes in order to feed drives,
or remove two tapes from adjacent drives which have unloaded them.  It does
make a difference.  Whether the difference is worth that much extra cost has
to be determined by how busy your system is and how much time costs your
company.  Keep in mind that tape shuffling by the robot constitutes only a small
fraction of the time that it takes a tape to become available:
load/unload/positioning times are usually substantial (a minute or more), being
the largest factor in data availability time.  A dual gripper shaves some
seconds off the overall time.  We happen to have a dual gripper, and our LM
stats show it being used about 40% of the time.

Looking in on your tape library with a stopwatch, with a TSM console nearby, is
a good way to see where time is consumed when data/service is requested and tape
work has to be done.  Your choice of tape drive technology is the major factor
in overall access speed.

   Richard Sims, BU