disk fragmentation

Jeremy Faulkner gldisater at gto.net
Tue Feb 1 12:56:45 PST 2005

Jim Pazarena wrote:
> during the boot sequence, I routinely see a "% fragmentation message".
> It was my understanding that fragmentation doesn't occur on a Unix
> (er FreeBSD) box..
> It seems that there is a concept of fragmentation from the above
> message, so, is there an "un-fragment" utility?
> Jim

No there is not a defragmenting program. Fragmentation is not a problem 
it is part of the normal operation of the filesystem.

Data is stored in the filesystem in blocks, if a file does not have 
enough data to evenly fill all of its assigned blocks then the last 
block for the file is a fragment. The UFS filesystem will fill the 
fragment with new data when new data is added to the file.

Some filesystems used by a redmond based company do not attempt to fill 
existing fragments, but simply add new blocks to the file so that a file 
could have more than one fragmented block.

There are better descriptions of what is occurring in the archives, and 
presumably in textbooks that discuss filesystems.

Jeremy Faulkner	<gldisater at gto.net>

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