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 ~/glibc214
cd ~/glibc214
wget http://ftp.gnu.org/gnu/glibc/glibc-2.14.tar.gz
tar zxvf glibc-2.14.tar.gz
cd glibc-2.14
mkdir build
cd build
../configure --prefix=/opt/glibc-2.14
make -j4
sudo make install
export LD_LIBRARY_PATH=/opt/glibc-2.14/lib
(for current login session) OR addLD_LIBRARY_PATH=/opt/glibc-2.14/lib
in the /etc/environment and performsource /etc/environment
(to add env variable permanently)