McGraw, Robert P wrote:

When I backup I would like all my larger size files to be put on the first
part of the tape and work down to the smaller size files toward the end of

the tape. This I believe and hope will provide better tape usage.

Yes, it does.

If large size files are dumped last to tape there is a good chance that it
will hit EOT and will then have to start over and a large chunk of tape will
have been wasted and so will time. If smaller size files are sent at the end
then if it does hit EOT not much tape is wasted.

I have been using "SSSSSSSSSS".

So my question:

1) dose Amanda get the size of all the backup files and then figure the
order that it will write to tape?

Amanda does an estimate of each DLE, and from those figures
decides on which dumps to choose first (dumporder).

2) will Amanda get the size of the tape and then figure the order that it
will write files to tape.

When taper is free to write the next dumpimage from holdingdisk
to tape, then the "taperalgo" parameter decides which image
from holdingdisk (only those that are completely done) is the
next onej to write to tape.

3) will Amanda do the dumps in the order that it needs to write to tape.

No.  Dumporder is independent of tapeorder.  But tapeorder
is influenced by the availability of finished dumps in the holdingdisk.
Dumps that bypass holdingdisk are always done last, even when,
and mostly because, they are (too) large (to fit in holdingdisk space).

See:

http://wiki.zmanda.com/index.php/How_To:Fill_tapes_to_100%25