There is IT in Helsinki

There is IT in Helsinki

Red Hat – Clustering and Storage Management – Course Objectives - part 2

Post 1 - https://www.guldmyr.com/red-hat-clustering-and-storage-management-course-objectives/ Where I checked out udev, multipathing, iscsi, LVM and xfs.

This post is about getting using luci/ricci to get a Red Hat cluster working, but not on a RHEL machine because sadly I do not have one available for practice purposes. So CentOS64 it is. Using openstack for virtualization.

Topology: Four hosts on all three networks, -a, -b and internal. Three cluster nodes and one management node.

Get the basic cluster going:

  • image four identical nodes
  • ssh-key is distributed
  • /etc/hosts file has all hosts, IPs and networks
  • network interfaces are configured -
  • set a gateway in /etc/sysconfig/network
  • firewall
  • all traffic allowed from -a and -b networks
  • at a minimum allow traffic from the network that the hostname corresponds to that you enter in luci
  • dns (PEERDNS=no is good with several dhcp interfaces)
  • timesync with ntpd
  • luci installed on mgmt-node # ricci is a web gui
  • ricci installed on all cluster nodes # this is the service talks with corosync
  • password set for user ricci on cluster nodes
  • create cluster in luci
  • multicast perhaps doesn't work so well in openstack ?
  • on cluster nodes this runs "yum -y install cman rgmanager lvm2-cluster sg3_utils gfs2-utils" if shared storage is selected, probably less if not.
  • fencing is really important, how to do it in openstack would require a bit of work though. Not as easy as with kvm/xvm to send a destroy domain message.

Tests:

  • Update and distribute cluster.conf
  • Have a service run on a node on the cluster (doesn't have to have a shared storage for this).
  • Commands:
  • clustat
  • cman_tool
  • rg_test test /etc/cluster/cluster.conf start service name-of-service
  • ccs_config_validate

Share an iSCSI target between all nodes:

  • Using management node to share the iSCSI LUN.
  • tgtd, multipath
  • clvmd running on all nodes
  • lvmconf - make sure locking is set correctly
  • create vg with clustering
  • partprobe; multipath -r # do this often
  • vgs/lvs and make sure all nodes see the clusterd lv
  • minimum GFS filesystem is around 128M - you didn't use all the vg right? =)
  • for testing/small cluster lowering the journal size is goodness
  • mount!