Ivan Voras ivoras at
Thu Mar 1 23:29:35 UTC 2007

Lowell Gilbert wrote:

> If you know the standard computer science terminology, it can be
> described quite tersely.  UFS fragmentation is a way of avoiding
> internal fragmentation from wasting too much space.  MS-DOS-FS
> fragmentation is an example of external fragmentation in the storage
> space.  They don't really have anything to do with each other.

It looks like I actually AM arguing about semantics here:

	"UFS fragmentation" refers to dividing blocks (e.g. 16KB in size) into
block fragments (e.g. 2KB in size) that can be allocated separately in
special circumstances (which all boil down to: at the end of files).
This is done to lessen the effect of internal fragmentation.

	"Fragmentation" without "UFS" prefix, as mostly used today (and which I
believe it's how the original poster understands it) refers to dividing
files into non-continuous regions, i.e. external fragmentation.

Correct so far?

"% fragmentation" message from fsck cannot refer to internal
fragmentation as the numbers don't add up, so it almost certainly refers
to external fragmentation.

As I understand it from technical documentation, it is correct that UFS
deliberately does external fragmentation of large files in order to make
file allocation faster and more managable, except in "optimized for
space" mode, correct? (the default being "optimized for time").

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