Schadenfreude-Mei: thx you very much for the valuable information.

GilaMonster i know that clustering is not for performence but i mention that cause i will use the third server for reporting and performance and i didn t want to use all of the three servers in the farm for clustering cause microsoft recommand to use 6 servers for as a perfect clustering moreover i want to keep the last server for reporting only as WAREHOUSE database (read only).