Some DBs are much more write than read, i have been experimenting with Solid State Hard disks lately to find out a bit of what can be gained from adding SSD drives to servers, here are the conclusions.
Do not use SSD to
Host database files where you will write plenty.
Log files are a giant no go
read large files
write large files
Do use SSD (After disabling ATIME)
Databases where you read far more than you write, DBs with mostly constant data
Small image files like the files that belong to a theme of a very popular website, for example the logo file that gets hit millions of times a day
Here are the results.
1- I have dissabled ATIME, with ATIME active, SSDs have almost no advantage in there best case, and a big disadvantage in there normal case, ATIME can be disabled in your FSTAB.
Also note that the above applies to a linux system, for a windows system, you can use delayed write to fix this.
testing 2 SSD drives, the INTEL SSD seems to have a superb controller, the other was miserable, caused the PC to hang including the mouse in certain tests
The other drive is NOT A SAMSUNG, i have heard many good things about the samsung drives, but unfortunatly i have no samsung drive to test, the sofware used for the testing is still setup, and once i get my hands on one i will let you know
In a certain application where small data is retreived from a database (MySQL) in every querry, and the number of rows on that database was in millions, The SSD disk was astonishingly faster, almost 10 times faster on the computer where it may have hit a threshold of some other limit (But i doubt it).
In short, get a good SSD drive, use it as prescribed above.
SSD disks are not the coolest (They are the coolest if you mean temprature) for many purposes, but they are cool for the applications described above.
SSD is not something i would use as my desktop hard disk, it may boot faster with all the reading that is done with no seek time, But other than booting faster, some slowness will pop up with big files and with disk writes, you have been warned, SSDs are not great for MOST desktop users
The advice offered for personal PCs and laptops is based on how i use a PC, there are generally nice improvements in battery power, but this was beyond the scope of my testing since i was testing with Servers in mind.