Tom Robinson wrote at 12:30 +1100 on Jan 22, 2009:
 > I've got several disks that are showing weird compression results in the 
 > amanda report. Here's one of them:
 > 
 >                                                    DUMPER STATS              
 >      TAPER STATS  
 > HOSTNAME DISK                      L   ORIG-KB     OUT-KB  COMP%  MMM:SS   
 > KB/s MMM:SS     KB/s
 > ------------------------------------ 
 > ------------------------------------------ ---------------
 > host     /disk                     1   2031690    4063380  200.0   36:34 
 > 1852.3   6:27  10487.2
 > 
 > 
 > Note the ORIG-KB blows out to twice the size! COMP% is 200.0...
 > 
 > This happens on more that one disk actually. I chose this disk as it's 
 > the biggest disk that I dump, it shows the most expansive blowout and I 
 > noticed it first. This disk uses 'compress NONE' (dumptype is 
 > nocomp-root). Some of the other disks showing compression weirdness are 
 > using 'compress client fast' in their DLE's.

Smells like a factor of two error somewhere (512 byte blocks vs. 1024?).
What does 'env -i du -ks /disk' say?