I thought that my MySQL InnoDB database was a bit slow, at least when running on an encrypted disk. Added a 80GB X25-M SSD disk to keep the MySQL database on (only development data so no encryption needed there). My performance increased 5 times as worst and more then 10 times at best.
Application with a lot of short database access (such as large update statements in mysql) will get a huge boost with SSD. We will see how it performs in the long run...
So far it is highly recommended!
Bind-mount is really good:
mount -B /media/SSD/mysql /var/lib/mysql
or in fstab:
/media/SSD/mysql /var/lib/mysql bind defaults,bind 0 0
Did all this to get up the speed when producing really large CRLs (>500.000 revoked certificates). Works pretty neat.