what is the meaning of "optimization changed from TIME to SPACE"

Bill Moran wmoran at potentialtech.com
Tue Feb 19 15:21:20 UTC 2008

In response to Brian <bri at brianwhalen.net>:

> ivan dimitrov wrote:
> > After upgrading from freebsd-5.5-R to 6.3-R, I get the following message in dmesg:
> >
> > "/storage/pub/www/ram: optimization changed from TIME to SPACE"
> >
> > I use a ram disk via the md driver.
> > Here is the line from my fstab file:
> >
> > md      /storage/pub/www/ram    mfs     rw,-s4m                 2       0
> >
> > Does this mean that there is some sort of error? ...and is there anything that can be done, so that I don't get this message in dmesg?
> >
> > Any help will be greatly appreciated :)

UFS normally optimizes file placement for performance.  Unfortunately,
in order to do this it has to write files in such a way that it
sometimes wastes some space.  When the partition gets close to full,
FreeBSD automatically switches to "space optimization" which doesn't
waste any space, but doesn't perform as well.

The short answer is, "This is happening because your partition is too
close to full.  It's not an error, but you should clean up some files
or add space."

It also has nothing to do with the difference between 5.5 and 6.3.

Bill Moran

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