Manually splitting large disks
You may happen to run into the problem of having to back up more data than will fit onto a single tape, like when you have partitions that are much larger as a tape. Over time, the partition will hold more and more data, and if you started with a simple amanda configuration that backs up the partition as a whole, backups will fail sooner or later. Your shiny tape changer isn't all that helpful with this because amanda doesn't automagically change to the next tape to continue writing on it (Upcoming versions of amanda might do that.).
Thus, the need arises to virtually split partitions into parts so that each part remains smaller than a tape. One way to do that is creating appropriate entries in the disklist.
Example
Let's assume that you have two large partitions, holding several directories and subdirectories like the following:
/home/ /home/andrew /home/anne /home/brian [...] /home/wanda /home/zeus /share/ /share/financial /share/financial/company-a /share/financial/company-b /share/reports
You created entries in your disklist to back them up:
largehost /home my-dumptype largehost /share my-dumptype
That worked fine, but now on each of the partitions, there's too much data to fit onto a single tape. You will have to split up the partitions to back them up.
Splitting it up, the easy part
Considering the /home partition, it becomes obvious that you could split it alphabetically. You would create disklist entries to back up each subdirectory by using wildcards. You also want to catch anything under /home that doesn't fit into the wildcard specifications, so there:
largehost /home_a /home { my-dumptype include "./a*" } 1
largehost /home_b /home { my-dumptype include "./b*" } 1 [...] largehost /home_w /home { my-dumptype include "./w*" } 1
largehost /home_z /home { my-dumptype include "./z*" } 1
# catch all the rest of /home: largehost /home_rest /home { my-dumptype exclude append "./[a-z]*" } 1
Notice the use of the 'include' and 'exclude' options. They do what you would guess, i. e. include the files specified, or exclude them. The tricky part is to use different disk names ('/home_a', '/home_b', ...) on the same partition/mount point ('/home').