What's wrong with backing store?

[Steffen Kluge]

Hi,
I've just got to ask this, please forgive me if it is only marginally
on-topic for this list.

Back when I started using X11 (late 80's, Ultrix, X11R3), turning on
save-unders and backing store was an essential performance tuning step,
that drastically improved the perceived "speed" of the desktop (e.g.
disappearing menus exposed the underlying window instantly, without it
having to be re-drawn).

I've used save-unders and backing store ever since. Which also means
that ever since starting to use RH desktops I had to turn it on
manually, by editing the X command line in [gx]dm.conf. All RH and FC
desktops I've used so far disable backing store (and at the same time
save-unders - the two seem to be inextricably linked) by default.

Why is that so? I have to admit that with modern hardware the perceived
speed-up is small and may even be entirely based on self-suggestion.
However, I'd like to understand the pros and cons of turning on backing
store with modern X servers and on modern hardware.

Cheers
Steffen.

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