Disk defragmenter in Linux

Les Mikesell lesmikesell at gmail.com
Sat Dec 31 18:15:32 UTC 2005

On Sat, 2005-12-31 at 03:12, Tim wrote:

> Unless fragmentation on ext3 file systems is a problem, and I've no
> evidence to the contrary, then it doesn't matter how the data is put on
> the drive.

All you have to do is look at the seek time on a disk drive
compared to any other computer operation to see what the
effect will be if a file that is normally read sequentially
is broken into non-contiguous chunks.  However aside from
the effort the system makes to avoid doing that, the real
reason you don't often notice the problem in practice is that
frequently-accessed files always live in cache so if you
read a file often you only take the speed hit once - and if
you don't read it often it probably doesn't matter.  Writes
also always go through cache and sensible operating systems
will sort the write-back into seek order to avoid threshing
the head around in the process.  So, if you think you have
a speed problem caused by your disk, the quick fix is normally
to add more RAM.

  Les Mikesell
   lesmikesell at gmail.com

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