Why the old Windows Defrag UI was inaccurate:
Say you have a 100GB volume.
To be truly accurate, defrag would display 1 colored bar for each cluster on
the volume (4k/cluster on most). Anything else is inaccurate.
Your screen may be about 1900x1280 pixels, so you can fit about 1900
clusters in the width of your screen, graphically.
You need about 26214400 bars of 1 cluster each to display your disk
accurately, cluster by cluster on your 100GB hard drive. (ie each cluster
that is free is white, each that is part of a fragmented piece of file is
red, and the rest are green or blue). If defrag took up your whole monitor,
we would need about 13797 rows of volume data to be accurate. That's a lot
to scroll through for a picture of the volume.
The old UI could be expanded to nearly screen width. So that means each bar
in the old UI, on a 100GB volume, would have been nearly 14000 clusters
(taken from row calculation above.)
That is to say, 54MB+.
Therefore, our UI was inaccurate. I don't know the calculation for a pixel
width in the old code....
BUT if for example, we went by "winner per pixel width", then one
single-pixel-width bar's color would be determined simply by whether there
was more free space, fragged space, non fragged space, or unmovable space.
So in the 54MB example, if 10MB was free space, 10MB was fragged space, and
10MB was unmovable, with the rest being non-fragmented space, the entire bar
would be blue. This problem is of course twice as bad with a 200GB volume.
With storage sizes increasing so quickly, there is not a good way to be
accurate enough to provide a decent picture. Admittedly, once defrag has
been running on a schedule on your computer for a while, the volume will be
largely separated into big blue and white chunks, but for less frequently
defragmented volumes, the UI is still no good.
**
You can view the accuracy problem yourself by resizing the defrag analysis
window in XP (in computer management) a few times and watching red bars
"magically" disappear with the resizing. Sometimes they even migrate. I
have one on an XP box that magically appears when the window is slightly
wider than my screen, in the middle of an otherwise "free" space.
**
As to 2nd question:
I can not speak for Microsoft as to the accuracy of other defragmenter UIs,
only our own.
