I'm trying to figure out why Amanda doesn't seem to ever do
incremental backups on any of my filesystems, even when I
have promotions disabled.

Here is an example of three successive runs for a particular
export I'm backing up.  The three lines below represent
backups from days 2003122[012], and I've included the column
headers so the data make sense:

    HOSTNAME                     DISK            L    ORIG-KB     OUT-KB COMP%  
MMM:SS    KB/s   MMM:SS
    +KB/s
    --------------------------------------------  
------------------------------------   --------------
    diabolus2.rwc.questra.com    /export/finance 0    4880940    4880940 --     
2:51 28509.6    13:07  6201.3
    diabolus2.rwc.questra.com    /export/finance 1    4880940    4880940 --     
2:40 30511.5    15:55  5111.4
    diabolus2.rwc.questra.com    /export/finance 1    4880940    4880940 --     
2:39 30651.0    15:48  5148.1

Notice how the size didn't change from the first day (level
zero) to the next (level 1).  I know for a fact the data on
disk for the second day did not change since the first day,
but for some reason Amanda is basically doing a complete
full dump anyways, when it should be doing nothing.

Here's the runtar outputs from these days:

    # grep finance runtar.2003122[012]*
    runtar.20031220020000.debug:running: /bin/tar: /bin/tar --create --file 
/dev/null --directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_0.new 
--sparse --ignore-failed-read --totals .
    runtar.20031220020002.debug:running: /bin/tar: /bin/tar --create --file 
/dev/null --directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_1.new 
--sparse --ignore-failed-read --totals .
    runtar.20031220020720.debug:running: /bin/tar: gtar --create --file - 
--directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_0.new 
--sparse --ignore-failed-read --totals .
    runtar.20031221020001.debug:running: /bin/tar: /bin/tar --create --file 
/dev/null --directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_0.new 
--sparse --ignore-failed-read --totals .
    runtar.20031221020002.debug:running: /bin/tar: /bin/tar --create --file 
/dev/null --directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_1.new 
--sparse --ignore-failed-read --totals .
    runtar.20031221020211.debug:running: /bin/tar: gtar --create --file - 
--directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_1.new 
--sparse --ignore-failed-read --totals .
    runtar.20031222020000.debug:running: /bin/tar: /bin/tar --create --file 
/dev/null --directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_0.new 
--sparse --ignore-failed-read --totals .
    runtar.20031222020001.debug:running: /bin/tar: /bin/tar --create --file 
/dev/null --directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_1.new 
--sparse --ignore-failed-read --totals .
    runtar.20031222020210.debug:running: /bin/tar: gtar --create --file - 
--directory /export/finance --one-file-system --listed-incremental 
/var/lib/amanda/gnutar-lists/diabolus2.rwc.questra.com_export_finance_1.new 
--sparse --ignore-failed-read --totals .

I'm basically at a loss as to why this is happening.
Someting must be screwy with my config because this is
happening for all of my DLEs; it seems to *always* do full
backups no matter what, even though it claims it is using
tar incremental levels > 0.

Here's the amanda.conf from this machine:

    tpchanger               "chg-zd-mtx"
    changerdev              "/dev/changer"
    tapedev                 "/dev/nst0"
    changerfile             "changer"
    diskfile                "disklist"
    tapelist                "tapelist"
    infofile                "/var/lib/amanda/normal/curinfo"
    indexdir                "/var/lib/amanda/normal/index"
    logdir                  "/var/log/amanda"

    dumpcycle               14 days
    runspercycle            14
    tapecycle               21 tapes
    runtapes                1
    includefile             "tapetype"
    tapetype                AIT-2

    netusage                inf
    taperalgo               largestfit
    dumporder               "TTTTTTTTTT"
    inparallel              10
    autoflush               on
    amrecover_do_fsf        on
    amrecover_check_label   on

    columnspec              
"HostName=0:-1,Disk=4:-1,Level=1:-1,OrigKB=2:9,OutKB=2:9,Compress=1:-1,DumpTime=2:<-1,DumpRate=1:7,TapeTime=3:-1,TapeRate=1:7"

    holdingdisk hold0 {
            comment         "13G(fs) holding space for normal set"
            directory       "/var/amanda/holdspace"
            use             0
            chunksize       0
    }

    define dumptype tardump {
            comment         "uses GNU tar"
            compress        none
            holdingdisk     yes
            ignore          no
            index           yes
            program         "GNUTAR"
            record          no
            starttime       0001
    }

here is the relevant DLE:

    diabolus2.rwc.questra.com /export/finance tardump

let me know if any further information might be useful.
Thanks for any help.