Tape usage extremely high

The most likely reason here - no accounting for encryption being used at the client side - is that your schedules are using different retention levels which cause each retention level to use a different tape

By this i dont mean different retention period as a retention period of 12 months using retention level 3 is actually different to a retention period of 12 months using retention level 4

Likewise infinite retentions by default go from level 9 to 20 but all are different and will write to different tapes

If this happened after an upgrade then perhaps previosuly you allowed multiple retentions per media (Master Host Properties) and the upgrade has reset that value

Give a little more detail about you policies / schedules / settings to see if we can dig deeper

Another reason for high media usage is lack of Media sharing. 

If you enable global media sharing, all media servers/appliances can append to the same tapes.

Without media sharing each media server requires own set of dedicated tapes.

Try to limit amount of volume pools as well.

What is the transfer rate from dedupe appliance to tape ?

If we go below the tape drive variable writing speed the tape drive will start to do "shoe-shining" (e.g. do start/stops). Each start/stop operation require a interblock gab to separate where writing ended to where writing start. That tiny space with no data may add up significant data capacity  if all the tape drive do is start/stops. 

https://en.wikipedia.org/wiki/Tape_drive (see techinical problems)

Thanks, Marianne.  I actually just noticed this morning that this possibility would really help us.  Where do I change that setting. I know I've seen it before and can find it again, but I'm sure you can point me in the right direction fatser. :)

Okay I actually found the setting.  I checked the "Enable Unrestricted Media Sharing for all media servers" box on the four media servers using the new library.  I did not check it on the master server because we have other media servers and libararies that I don't want to use that setting for.  Does this sound okay to you?

Actually we only use two retention periods and they are set in the SLP.  For daily diffs and weekly fulls we use 1 month and for monthly fulls we use 1 year.  Even on the nights when we have no monthlies running we are still kicking out at least ten tapes that have under 1 TB written to them.  I also wonder about changing the parameters for the SLP duplication session. I believe we chose the default which is 5 minutes. Should that timeframe be increased?

I thought that setting was only available on the Master server and it allows all media servers and NDMP hosts to share media

For this to work you should not have any Media Sharing groups settup

If you want just four Media Servers to share media then you should use a media server group for media sharing and add just those four servers to the group

Okay I undid that setting and set up the media sharing group for those four media servers.  Now do I need to change any of the storage unit settings?

That should be all you need to do - although a fresh load of expired tapes will help as any already used may already be owned by individual servers

You can see their status in the robot section under media if you add the Media Owner and Server Group columns you will see if the tapes can be used by the group or not

Hope this helps