In computer
disk terminology, fragmentation is the
process or condition of files that are composed of more
than one
extent. Fragmentation of this sort is bad,
as it will increase the amount of
head motion needed
to read the file, and thus slow things down.
Poorly optimized operating systems occasionally need to be
defragmented to increase performance.
Alternately, in the BSD fast filesystem (also in UFS),
a fragment is a block that has been subdivided to
hold tail ends of several files that would otherwise
each take up an entire block. This kind of fragmentation
is a Good Thing.
Just to be confusing, both meanings of fragmentation
are used when refering to unix filesystems.