It doesn't make much sense to use SSD drives for web-hosting - the content, which is being served to visitors is static and in most cases cached in RAM of the server.
SSD drives make much sense on mail servers, where a lot of I/O operations are happening during normal operation.
The difference between magnetic HDDs and SSD HDDs is several times faster sequential write (120 MBps on magnetic, 600 MBps on SSD) and much shorter random access times.
To test your server's HDD for sequential write speed do this on the linux console:
dd if=/dev/zero of=/zerofile bs=16M count=128 conv=fdatasync
When this command finishes, it shows the real sequential write speed of your HDD.
Regards,
catcher