You need to install glibc alongside your current installation of glibc as you cannot update to glibc 2.14 directly in centos 6.x safely. Follow the steps below to install glibc 2.14:
mkdir ~/glibc214cd ~/glibc214wget http://ftp.gnu.org/gnu/glibc/glibc-2.14.tar.gztar zxvf glibc-2.14.tar.gzcd glibc-2.14mkdir buildcd build../configure --prefix=/opt/glibc-2.14make -j4sudo make installexport LD_LIBRARY_PATH=/opt/glibc-2.14/lib(for current login session) OR addLD_LIBRARY_PATH=/opt/glibc-2.14/libin the /etc/environment and performsource /etc/environment(to add env variable permanently)