is Raid 1 (mirror) so slow ?

I'd like to get more stability and fast recovery for my server. So i decide to make RAID 1 (mirror) using 2 SATA hd, since using raid 1 i almost dont have to worry about hardisk failure. I want to use RAID 5 using 3 HD but this will cost me more. The server will running java using tomcat, and mysql db. But our vendor said that using RAID 1 is slower then using 1 HD. Is this true ? If i use as application server using database, would be enough ? Another thing, I use softraid from yast. -- Arie Reynaldi Zanahar reymanx at gmail.com http://www.reynaldi.or.id