Criar QuorumDisk

RHCS(Red Hat Cluster Suite) quorum disk The last post "RHCS I/O fencing" is about dealing with split-brain situation, in which cluster members lost heartbeat communication and each believe it is legitimate to write data to the shared storage. Methods to deal with split-brain situation: 1. Redundant heartbeat path network port communication plus serial port communication 2. I/O fencing Remaining nodes separate failed node from its storage either by shutdown/reboot power port or storage port 3. Quorum disk Quorum disk is a kind of I/O fencing, but the reboot action is executed by failed node's own quorum daemon. It also has additional feature: contributing vote to cluster. if you want the last standing node to keep the multiple-nodes cluster running, quorum disk appears to be the only solution. RHCS (Red Hat Cluster Suite) Quorum disk facts - A shared block device (SCSI/iSCSI/FC..), Device size requirement is approximately 10MiB - Supports maximum 16 nodes, nodes id must be sequentially ordered - Quorum disk can contribute votes. In multiple nodes cluster, together with quorum vote, the last standing node can still keep the cluster running - single node votes+1 <=Quorum's disk vote < nodes total votes - The failure of the shared quorum disk won’t result in cluster failure, as long as Quorum's disk vote < nodes total votes - each node write its own health information in its own region, the health is determined by external checking program such as "ping" Setup Quorum disk

1. initialise quorum disk once in any node

mkqdisk -c /dev/sdx -l myqdisk Add quorum disk to cluster Use luci or system-config-cluster to add quorum disk, following is the result xml file <clusternodes> <clusternode name="station1.example.com" nodeid="1" votes="2"> <fence/> </clusternode> <clusternode name="station2.example.com" nodeid="2" votes="2"> <fence/> </clusternode> <clusternode name="station3.example.com" nodeid="3" votes="2"> <fence/> </clusternode> </clusternodes>

1. expected votes =9=(nodes total votes + quorum disk votes) = (2+2+2+3)

<cman expected_votes="9"/>

1. Health check result is writen to quorum disk every 2 secs
2. if health check fails over 5 tko, 10 (2*5) secs, the node is rebooted by quorum daemon
3. Each heuristic check is run very 2 secs and earn 1 score,if shell script return is 0

<quorumd interval="2" label="myqdisk" min_score="2" tko="5" votes="3"> <heuristic interval="2" program="ping -c1 -t1 192.168.1.60" score="1"/> <heuristic interval="2" program="ping -c1 -t1 192.168.1.254" score="1"/> </quorumd> Start quorum disk daemon The daemon is also one of daemons automatically started by cman service qdiskd start Check quorum disk information $ mkqdisk -L -d mkqdisk v0.6.0 /dev/disk/by-id/scsi-1IET_00010002: /dev/disk/by-uuid/55fbf858-df75-493b-a764-5640be5a9b46: /dev/sdc: Magic: eb7a62c2 Label: myqdisk Created: Sat May 7 05:56:35 2011 Host: station2.example.com Kernel Sector Size: 512 Recorded Sector Size: 512 Status block for node 1 Last updated by node 1 Last updated on Sat May 7 15:09:37 2011 State: Master Flags: 0000 Score: 0/0 Average Cycle speed: 0.001500 seconds Last Cycle speed: 0.000000 seconds Incarnation: 4dc4d1764dc4d176 Status block for node 2 Last updated by node 2 Last updated on Sun May 8 01:09:38 2011 State: Running Flags: 0000 Score: 0/0 Average Cycle speed: 0.001000 seconds Last Cycle speed: 0.000000 seconds Incarnation: 4dc55e164dc55e16 Status block for node 3 Last updated by node 3 Last updated on Sat May 7 15:09:38 2011 State: Running Flags: 0000 Score: 0/0 Average Cycle speed: 0.001500 seconds Last Cycle speed: 0.000000 seconds Incarnation: 4dc4d2f04dc4d2f0 The cluster is still running with last node standing Please note Total votes=quorum votes=5=2+3, if quorum disk vote is less than (node votes+1), the cluster wouldn’t have survived $cman_tool status .. Nodes: 1 Expected votes: 9 Quorum device votes: 3 Total votes: 5 Quorum: 5 .. POSTED BY HONGLUS AT 5:12 PM