yum-fastestmirror 清除缓存： rm /var/cache/yum/timedhosts.txt
修改 /etc/yum.repos.d/epel.repo
mirrorlist=http://mirrors.fedoraproject.org/mirrorlist?repo=epel-5&arch=$basearch
mirrorlist=http://mirrors.fedoraproject.org/mirrorlist?repo=epel-5&country=us&arch=$basearch