Re: fragmentation

[Konrad Heuer <kheuer@xxxxxxxxxxxxxx>]

On Thu, 24 Sep 1998, Peter Kok wrote:

> After boot up a computer, there is message prompted
> 
> /dev/rmd0s2a: clean, 17705 free (313 frags, 2174 blocks, 1.0
> fragmentation)
> 
> what is the meaning of frags?  and how do you do defragmentation? 

You don't need to defragment a FreeBSD file system (which is essentially a
4.2BSD fast file system (ffs)).

The file system typically uses 8K blocks of disk space. Since files are
often smaller a file can use fragments (typically 1K) of a block. To be
more precise, the last block of a file may be fragmented.

Fragmentation you probably think of is spreading all the blocks of a file
over the disk. The Berkeley ffs implements very intelligent algorithms to
prevent this and to optimize file system throughput. 

Take a look at the system documentation:
gunzip < /usr/share/doc/smm/05.fastfs/paper.ascii.gz | more

Regards
Konrad Heuer

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