Defrag.

[Dave Mitchell]

On Thu, Oct 06, 2005 at 10:05:26PM +0700, Strong wrote:
> On Thu, 2005-10-06 at 23:18 +0930, Tim wrote:
> > As Andy said, the need for defragging isn't there.
> How is it if when checked it says there are fragmentation, unorganized
> or whatever?

These are two different things.

Fragmentation, in the Windows sense, is where one file is stored as lots
of small blocks spread all over the disk. Accessing the whole file becomes
very slow.

Fragmentation, in the UNIX fsck sense, is the percentage of big blocks (eg
8k) that have been split into small (eg 1K) subblocks to allow for the small
chunk of data at the end of a file to be stored efficiently. For example,
a file that is 18K in size will use two 8K blocks plus a 2K chunk of an
8K block that has been split. Fragmentation is this sense is harmless,
and just indicates that the OS isn't wasting disk space. Or to put it
another way, if you filled your disk with 1k files, fragmentation would
be reported as 100%.

(Well, that's the case with traditional UNIX filesystems like UFS;
I should imagine xfs and raiserfs do things differently).


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