yum update fails > Error: Cannot retrieve repository metadata (repomd.xml) for repository: powerstack. Please verify its path and try again

I'm trying to do yum update on my production server which is ended by throwing an error, this is what it returns for that command -

Loaded plugins: fastestmirror, security
Setting up Update Process
Loading mirror speeds from cached hostfile
 * base: mirrors.rit.edu
 * epel: fedora-epel.mirrors.tds.net
 * extras: mirrors.rit.edu
 * updates: mirrors.rit.edu
 * webtatic: us-east.repo.webtatic.com
http://download.powerstack.org/6/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'download.powerstack.org'"
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: powerstack. Please verify its path and try again

I've tried command yum clean all which returns this -

Loaded plugins: fastestmirror, security
Cleaning repos: base epel extras longview mod-pagespeed newrelic powerstack updates varnish-3.0 webtatic
Cleaning up Everything 

This is my yum config (/etc/yum.conf)

[main]
cachedir=/var/cache/yum/$basearch/$releasever
keepcache=0
debuglevel=2
logfile=/var/log/yum.log
exactarch=1
obsoletes=1
gpgcheck=1
plugins=1
installonly_limit=5
bugtracker_url=http://bugs.centos.org/set_project.php?project_id=16&ref=http://bugs.centos.org/bug_report_page.php?category=yum
distroverpkg=centos-release

#  This is the default, if you make this bigger yum won't see if the metadata
# is newer on the remote and so you'll "gain" the bandwidth of not having to
# download the new metadata and "pay" for it by yum not having correct
# information.
#  It is esp. important, to have correct metadata, for distributions like
# Fedora which don't keep old packages around. If you don't like this checking
# interupting your command line usage, it's much better to have something
# manually check the metadata once an hour (yum-updatesd will do this).
# metadata_expire=90m

# PUT YOUR REPOS HERE OR IN separate files named file.repo
# in /etc/yum.repos.d
multilib_policy=best

This is /etc/yum.repos.d/epel.repo config -

[epel]
name=Extra Packages for Enterprise Linux 6 - $basearch
#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
mirrorlist=http://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6

[epel-debuginfo]
name=Extra Packages for Enterprise Linux 6 - $basearch - Debug
#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch/debug
mirrorlist=http://mirrors.fedoraproject.org/metalink?repo=epel-debug-6&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
gpgcheck=1

[epel-source]
name=Extra Packages for Enterprise Linux 6 - $basearch - Source
#baseurl=http://download.fedoraproject.org/pub/epel/6/SRPMS
mirrorlist=http://mirrors.fedoraproject.org/metalink?repo=epel-source-6&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
gpgcheck=1

I can't install any package either, throws the same error. Appreciate your help. Thanks

This error shows that your machine couldn't connect to repository powerstack. To update your system, you could disable it in file /etc/yum.repos.d/powerstack.repo by changing enable from 1 to 0 or run `yum update --disablerepo=powerstack*"