HDD does not work up to capacity

Daniel Bye dan at slightlystrange.org
Fri Jun 13 04:49:21 PDT 2003

On Fri, Jun 13, 2003 at 01:32:32PM +0200, freebsd_deamon at gmx.net wrote:
> this might be an incredible stupid question but since i am not that familiar
> with disk geometry i ask it anyway:
> I just bought an Hitachi DeskStar 180GXP HDD (it's the same as IBM) which is
> supposed to have a capacity of 61.4 GB but i can only get approx 58 to 59
> out of it.

This is normal.  UNIX systems tend to reserve a certain amount of the disk.
Below is an excerpt from man tunefs(8), which gives a good explanation:

    -m minfree
         Specify the percentage of space held back from normal users; the
         minimum free space threshold.  The default value used is 8%.
         This value can be set to zero, however up to a factor of three in
         throughput will be lost over the performance obtained at a 10%
         threshold.  Settings of 5% and less force space optimization to
         always be used which will greatly increase the overhead for file
         writes.  Note that if the value is raised above the current usage
         level, users will be unable to allocate files until enough files
         have been deleted to get under the higher threshold.

> why?
> is there a way arounf it?

There is, but I refer you to the excerpt above - you will lose performance if
you alter the default settings.  If you really want to do it, then read the
relevant man pages (newfs, tunefs, et al.) so you get a good understanding of
what you are doing, and why it's not necessarily a Good Thing...


Daniel Bye

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