At my site we use a very large TS3584 library (42 LTO5 drives) driven by NetBackup 6.5.6 running on Solaris.

The library is configured for ALMS.

The quantity of backup data being written to tape is somewhere in the neighborhood of 60-70 TB per day.

I am puzzled by the frequency with which the library feels it needs to clean the drives. On a given day, it is not uncommon for six (6) cleaning requests to be issued (i.e., six of the 42 drives request cleaning, per day.)

I trust the opinions of my coworkers who claim this is 'normal', but meanwhile the IBM CE who comes out to replace the drives regularly feels there is something wrong with this picture.

Has anybody else experienced similar behavior, and what is/was the resolution?