Ivan Voras ivoras at
Thu Mar 1 22:05:23 UTC 2007

Bill Moran wrote:
> In response to Ivan Voras <ivoras at>:

>> 352462 files, 2525857 used, 875044 free (115156 frags, 94986 blocks,
>> 3.4% fragmentation)

> Just to reiterate:
> "Fragmentation" on a Windows filesystem is _not_ the same as "fragmentation"
> on a unix file system.  They are not comparable numbers, and do not mean
> the same thing.  The only way to avoid fragmentation on a unix file system
> is to make every file you create equal to a multiple of the block size.

Ok, my point was that 3.4% is a low number for a long used system, but,
for education sake, what is the difference between Windows'
"fragmentation" and Unix's "fragmentation"?

I believe that a "fragmented file" in common usage refers to a file
which is not stored continuously on the drive - i.e. it occupies more
than one continuous region. How is UFS fragmentation different than
fragmentation on other kinds of file systems?

UFS has cylinder groups, blocks and block fragments. Obviously, a file
larger than a cylinder group will get fragmented to spill over to
another cylinder group. Block fragments only occur at the end of files.

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