SSD as a cheaper RAM

For RAID 10:can get 8* (Dell 1TB 7.2K SATA Hard Drive for PowerEdge R710,239$) for 8*239$=1912, which is ~1.86$ per GB

For SSD :can get 40GB card for 89$, which is ~2.2$ per GB

For memory: can get 4GB card for 33$,which is ~8.25$ per GB

(this picture cross-post from http://www.anandtech.com/show/4244/intel-ssd-320-review)

The performance test report as following:

(these pictures cross-post from  http://www.ssdperformanceblog.com/2011/07/intel-320-ssd-read-performance/)

As conclusion, this card provides great read performance.

A single card provides 5-8x better throughput and 10-14x better response time. Striping helps to increase throughput in 8-10x and response time in 10-22x.

Following is good articles for SSD URLS:

http://codemonkey.ravelry.com/2011/05/09/so-you-want-to-run-mysql-on-ssds/
http://www.ssdperformanceblog.com/
http://www.anandtech.com/show/4244/intel-ssd-320-review
http://yoshinorimatsunobu.blogspot.com/2009/05/tables-on-ssd-redobinlogsystem.html