Does amanda only backup changes to files?

[Dean Pullen]

Hi again.

I've been using amdump manually to test Amanda, and am backing up a full
disk's file system (/dev/sda). The first time its run it produces a report
with several gigabytes worth of backup:

USAGE BY TAPE:
  Label              Time      Size      %    Nb
  VFDailySet01       0:08    3393.4    4.1     1

Repeating runs on the same tape after this backup, seems to produce very
tiny backups:

USAGE BY TAPE:
  Label              Time      Size      %    Nb
  VFDailySet01       0:00       0.2    0.0     1

Does amanda only save 'changes' to files, or is something incorrect
happening here?

Dean