Too late. I usually re-installs the OS X to my MBP every one or two month. Not to mention when installing the OS, i have a habbit of "Zero Out Data".
You should get over both of these habits. Neither one offers any benefit at all.
How do you do that???
You have to set the upper limit of your browser's cache size to a very low figure, ideally zero. Of course this will slow your browser down.
What exactly is "scratch disk"? I think I have seen that term when I was using FCE4.
A scratch disk is just like the pad on which you scribbled the notes and calculations you didn't need to hand in when you took math tests in school (if you're old enough to remember pencil and paper). It's a place for certain applications to write temporary files as part of their normal operations. An app that uses a scratch disk generally allows you to designate one in its preferences. If you have just one disk connected to your computer, that one is used as the scratch disk. If you have more than one connected, you get to choose which one is used. Don't choose your SSD.
So, if SSD/FLASH have so many limititions, why people want them? Just because they run faster?
Yes, and because the people selling SSDs don't advertise the limitations.
The price is also too high.
True. Very true.
What's TRIM?
I'll let Wikipedia answer this one:
http://en.wikipedia.org/wiki/TRIM
If SSD is so vulnarable, who would use them?
People whose preferred operating systems support TRIM. People whose operating systems don't support TRIM, but who've heard that SSDs are fast and haven't done enough homework to understand what the lack of TRIM means. People with more money than sense.
One more question, is there any way that can make SSD and SATA2 work together? Like the 27" iMac, that uses SSD & SATA2. But how do we set it up? Will it be tedious to change the setting for all the programs?
Sorry, I don't understand what you're asking here.