I have done dumps of the filesystems of 3 machines to a common tape drive,
an Exabyte EXB-8500. One machine contains the tape drive, the other two use
rmt. Five tapes were filled (5GB each), with a sixth only partly used.
Next I wanted to test overwrite handling, as I was having problems with an
earlier version of xfsdump. I started a dump of a 75GB filesystem, without
using the -o flag. I began with the partly used sixth tape. The previously
used dumps had apparently left a stream terminator at media file 12, and
this is where the dump began.
After the tape became full, a tape change was requested. I either felt like
testing xfsdump, or I wasn't thinking clearly, so I accepted the tape change
request without changing the tape. As I watched "xfsdump: preparing drive",
the tape was rewound, and media files were examined. I was shocked to see
it continue dumping at media file 12 *again*. It found a stream terminator,
and that was all it was waiting for!
I noticed a bug was fixed in 2.2.13 regarding handling multiple backups to a
single tape, but I'm not sure what the exact problem was that was fixed.
The earlier dumps on the tapes were with the older version, 2.2.11-1, and
the *dump in question* was with 2.2.14-1.