How can Ubuntu behave more quickly on a USB stick than installed?

Question

I have a little question about my fresh installation of Ubuntu 12.10 on a Dell XPS 15z (Intel i7, 8 Go RAM, Nvidia GeForce something and an SSD (256 Go).

A few months ago, I installed Ubuntu 12.04 and it was perfect, without any lag or something. Great! Then I uninstalled it.

On Monday, I tried Ubuntu 12.10 with a live USB and it was perfect, fast, Unity 3D enabled, no lags... Great! (Except that I had to boot with the acpi=noirq option, as I read ot on the wiki and as I did before with Ubuntu 12.04.)

Then I decided to install it on my computer. No problems, all went perfeclty fine. When Grub appeared, I enabled the acpi=noirq and... blank screen. I know people have already encountered this bug so I won't go further. (With the acpi=off all was fine, but no battery manager.)

I logged in, no problem. And once the desktop open, all become laggy! It became unusable!

Animations very slow, crachs of Compiz very often...

My question is: How is this possible? How Ubuntu can be slower once installed than on a USB device? And how a newer version can be completely slower (and unusable) than the previous version?

EDIT

How do I turn off compiz ? killall compiz?

Answer 1

When you install it..Startup applications get added..they make booting a bit longer.

What i did was introduced a shell script that did this job of starting the startup apps but with a delay.

So now in my startup apps,i have just 2 scripts...they start,execute a delay and then progresively start otherapps.

Also compiz is a major reason why ubuntu gets slower! I dont know why!

Also resorting to diabeling networking before shut down will boot the system a biiit faster...

Also,for your question about why 12.10 is slower, Ubuntu becomes stable over a period of time.

As it is open source and has a pretty fast release cycle(of 6 months) the bugs that were not either exactly encountered during beta tests(as not all use beta) and the ones not fixed untill released(though such things are not introduced untill complete mostly).

As the users all over use Ubuntu,new problems and bugs are found and fixed.Even 12.04 was not perfect at release. It became better over a period of about 2 months after the exact release and so do the other versions.Also, 12.04 being LTS(5 yrs) will recieve more stability as many users prefer staying there.