Two-Node Fedora 14 cluster.conf
Revision as of 05:02, 6 March 2011 by Digimer
- See here for a more complete list of cluster.conf options.
This is the /etc/cluster/cluster.conf file used in the Two Node Fedora 13 Cluster.
Note: This is used in a generic node and should be safe to use and adapt for any 2-node cluster.
<?xml version="1.0"?> <!-- The cluster's name is "an-cluster" and, as this is the first version of this file, it is set to version "1". Each time this file changes in any way, the version number will have to be incremented by 1. NOTICE: Do not trust this document until all "Q." are answered and removed. NOTICE: This is a work in progress and likely contains errors and ommisions. --> <cluster name="an-cluster" config_version="14"> <!-- The Cluster Manager --> <!-- Options must be combined in one <cman... /> statement. If we had no need for cman arguments, we'd just put in the self-closing argument: --> <!-- <cman/> --> <!-- This allows you to configure a cluster with only two nodes. Normally, the loss of quorum after one of two nodes fails prevents the remaining node from continuing (if both nodes have one vote.). The default is '0'. To enable a two-node cluster, set this to '1'. If this is enabled, you must also set 'expected_votes' to '1'. --> <!-- <cman two_node="1" /> --> <!-- This is used by cman to determine quorum. The cluster is "quorate" if the sum of votes of members is over half of the expected votes value. By default, cman sets the expected votes value to be the sum of votes of all nodes listed in cluster.conf. This can be overriden by setting an explicit 'expected_votes' value. When using the 'two_node' value to '1' then this must be set to '1' as well. Please see 'clusternode' in the '<cluster...>' section for more info. --> <!-- <cman expected_votes="1" /> --> <!-- Set this to 'yes' when you are performing a rolling updade of the cluster between major releases. Q. Does this mean cman version, distro version, ...? --> <!-- <cman upgrading="no" /> --> <!-- This option controls cman's "Disallowed" mode. Setting this to '1' may improve backwards compatibility. The default is '0', disabled. Q. How and where exactly? --> <!-- <cman disallowed="0" /> --> <!-- This is the number of milliseconds after a qdisk poll before a quorum disk is considered dead. The quorum disk daemon, qdisk, periodically sends "hello" messages to cman and ais, indicating that qdisk is present. If cman doesn't receive a "hello" message in the time set here, cman will declare qdisk dead and generates error messages indicating that the connection to the quorum device has been lost. Q. Are quorum disks still useful? --> <!-- <cman quorum_dev_poll="50000" /> --> <!-- This is number of milliseconds to wait for a service to respond during a shutdown. Q. What happens after this time? Q. Does this refer to crm/pacemaker controlled services or any service? --> <!-- <cman shutdown_timeout="5000"/> --> <!-- no info. --> <!-- <cman ccsd_poll="1000"/> --> <!-- no info. --> <!-- <cman debug_mask="?"/> --> <!-- no info. Is this for the primary totem ring? --> <!-- <cman port="?"/> --> <!-- no info. --> <!-- <cman cluster_id="?"/> --> <!-- Enable stronger hashing of cluster ID to avoid collisions. Q. How? What is an example value? --> <!-- <cman hash_cluster_id=""/> --> <!-- Local node name; this is set internally by cman-preconfig and should never be set unless you understand the reprocusions of doing so. It is here for completeness only. --> <!-- <cman nodename="?"/> --> <!-- Enable 'cman' broadcast. To enable, set this to 'yes'. The default is 'no', disabled. Q. Under what conditions would this be enabled? --> <!-- <cman broadcast="no"/> --> <!-- No info. --> <!-- <cman keyfile="?"/> --> <!-- No info. --> <!-- <cman disable_openais="?"/> --> <!-- This provides the ability for a user to specify a multicast address instead of using the multicast address generated by cman. If a user does not specify a multicast address, cman creates one. It forms the upper 16 bits of the multicast address with 239.192 and forms the lower 16 bits based on the cluster ID. Q. Does this have to do with the totem ring? Q. What generates the cluster ID when it's not specified by the user? --> <!-- <cman multicast=""/> --> <!-- This is where you can define a multicast address. If you specify a multicast address, ensure that it is in the 18.104.22.168/16 network which cman uses. Using a multicast address outside this range is untested. Q. Is this for the first totem ring? --> <!-- <cman addr=""/> --> <!-- Usage examples for the 'cman' argument. --> <!-- This example shows the use of cman arguments to setup a two-node cluster. --> <cman two_node="1" expected_votes="1" /> <!-- Totem Ring and the Redundant Ring Protocol --> <!-- This controls the OpenAIS message transport protocol. Q. Does this also control corosync? Q. Are there specific arguments for either? --> <!-- This defines how many millisecond to wait for consensus. If this timout is reached, the cluster will give up and attempt to form a new cluster configuration. The default is '200' (0.2 seconds). --> <!-- <totem consensus="200"> --> <!-- This tells the totem protocol how long to wait, in milliseconds, for JOIN messages to come from nodes. The default is '100' (0.1 seconds). --> <!-- <totem join="100"> --> <!-- This sets the maximum amount of time, in milliseconds, the totem protocol will wait for a token. If this time elapses, the cluster will reformed which takes approximately 50 milliseconds. The reconfiguration time is, then, a sum of this value plus the reconfigure time. The default value is '5000' (5 seconds). --> <!-- <totem token="5000"> --> <!-- no info. --> <!-- <totem fail_recv_const=""> --> <!-- This controls how many times the totem protocol will attempt to retransmit a token before giving up and forming a new configuration. If this is set, 'retransmit' and 'hold' will be calculated automatically using 'retransmits_before_loss' and 'token'. --> <!-- <totem token_retransmits_before_loss_const=""> --> <!-- This attribute specifies the redundant ring protocol mode. It can be set to 'active', 'passive', or 'none'. Active replication offers slightly lower latency from transmit to delivery in faulty network environments but with less performance. Passive replication may nearly double the speed of the totem protocol if the protocol doesn't become cpu bound. The final option is 'none', in which case only one network interface is used to operate the totem protocol. If only one interface directive is specified, 'none' is automatically chosen. If multiple interface directives are specified, only 'active' or 'passive' may be chosen. NOTE: Be sure to set this if you are using redundant rings! NOTE: If you wish to use a redundant ring, it must be configured in NOTE: each node's <clusternode...> entry. See below for an example. --> <!-- <totem rrp_mode="passive"> --> <!-- This attribute specifies whether HMAC/SHA1 authentication should be used to authenticate all messages or not. It further specifies that all data should be encrypted with the sober128 encryption algorithm to protect data from eavesdropping. This can be 'on' or 'off'. The default is 'on'. If the totem ring is on a private, secure network, disabling this can improve performance. Please test to see if the extra performance is worth the reduced security. Q. Is the default actually 'on'? --> <!-- <totem secauth="on"> --> <!-- no info --> <!-- <totem keyfile=""> --> <!-- *** I don't think this is right. <interface ...> is not used. Instead, ring 0 uses the subnet that <clusternode name="..."> resolves to. The '<altname ...>' attribute sets the subnet that ring 1 uses. *** *** Left in until confirmed that this is wrong. Totem 'interface' arguments: You can specifiy one or two '<interface...>' arguments within '<totem...></totem>'. --> <!-- <totem ...> "ringnumber" is '0' or '1' and defines the ring as the primary or secondary ring. Currently, only two rings are supported. "bindnetaddr" must match the subnet of the interface you want the ring to use. The final octal must be '0'. This can be an IPv6 address, however, you will be required to set the 'nodeid' in the '<totem...>' section above. Further, there will be no automatic interface selection within a specified subnet as there is with IPv4. "mcastaddr" is the multicast address used by the totem protocol. Avoid the '22.214.171.124/8' range as that is used for configuration. If you use an IPv6 address, be sure to specify a 'nodeid' in the 'totem' directive above. "mcastport" is the UDP port used with the multicast address above. "broadcast" is not defined... <interface ringnumber="0" bindnetaddr="192.168.1.0" mcastaddr="126.96.36.199" mcastport="5405" broadcast="" /> </totem> --> <!-- Quorum Daemon --> <!-- Options must be combined in one <quorumd... /> statement. --> <!-- In older versions of RHCS, a quorum partition was used to maintain quorum with the network acting as a fall back. This eventually faded out of fashion and quorum disk partitions were rarely used. Today, quorum partitions are still not required but they are coming back into fashion as a way to improve the reliability of a cluster in a multiple failed state and to provide more intelligent quorum. Lets look at a couple of examples; 1. If you have a four-node cluster and two nodes fail, the surviving two nodes will not have quorum because normal quorum requires a majority (n/2+1). In this case, your cluster would shut down when it could have kept going. Adding a quorum disk would have allowed the surviving two nodes to maintain quorum. 2. If you have a four-node cluster and a network event occured where only one node retained access to a critical network, you would want that one node to proceed and you would rather fence the three nodes that lost access. Under normal IP quorum, the opposite would happen because, by simple majority, the one good node would be fenced by the three other nodes. The quorumd daemon can have huristics added. In this case, we would configure each node's quorumd to first check that critical network connection. The three nodes would see that they'd lost the link and remove themselves from the cluster. In this way, only the one good node would remain up and win quorum thanks to the votes assigned to the quorum disk. In short, the quorum disk allows a much more fine grained control of quorum in corner-case failure states. This section is not required and can be left out when you aren't using a quorum disk partition. A quorum partition cannot be used in clusters greater than 16 nodes. This is due to the latency caused be clusters larger that 16 nodes causing unreliable quorum disks. With 17 or more nodes, you must use IP-based (totem protocol) quorum only. A quorum disk must be a raw 10MB or larger (11MB recommended) partition on an iSCSI or SAN device. It is recommended that your nodes use multipath to access the quorum disk. You can not use a CLVM partition. Q. On a 2-node DRBD partition, can a raw 10MB partition be used? This is probably irrelevant as there is the 'two_node' cman option, but might be useful for the heuristics in a split brain. See: http://magazine.redhat.com/2007/12/19/enhancing-cluster-quorum-with-qdisk/ --> <!-- This controls how often, in seconds, that the quorum daemon on a node will attempt to write it's status to the quorum disk and read the status of other nodes. The higher this value is, the less chance that a transiant error will disolve quorum. The longer it will take to detect and recover from a failure. The default is '2'. Please see the '<heuristics...>' section below for heuristics interval. Q. Is this accurate? Q. Does this control the huristics or disk poll? --> <!-- <quorumd interval="2" /> --> <!-- If a node fails the heuristics checks and/or fails to contact the quorum disk after this many intervals, it will be declared dead and will be fenced (a "Technical Knock Out"). To determine how long this will actually take, multiple 'interval' by 'tko' and you will have the value is seconds. If you are using Oracle RAC, be sure that this and the 'interval' value are high enough to give the RAC a chance to react to a failure first. So if your RAC timeout is set to 60 seconds, and you are using the default 'interval' of '2', it is recommended to set this to at least '35' (70 seconds). Q. Is there a modern variant on the 'cman_deadnode_timeout' and, if so, does interval*tko still need to be lower? --> <!-- <quorumd tko="" /> --> <!-- This is the number of votes assigned to the quorum disk. This value should be the total number of votes of your cluster minus the minimum number of nodes your cluster can operate with. For example, if you have a four-node cluster that can operate with just one node, you would set this to '3' (4-1). This value must be set when using a quorum disk as there is no default. Q. Is this true, or would the votes be calculated? --> <!-- <quorumd votes="" /> --> <!-- The minimum score for a node to be considered alive. If omitted or set to 0, the default function, floor((n+1)/2), is used, where n is the sum of the heuristics scores. The Minimum Score value must never exceed the sum of the heuristic scores. If set higher, it will be impossible for the heuristics tests to pass. If the resulting score is below this value, the node will reboot to try an return in a better state. Q. Does it reboot after one failure? --> <!-- <quorumd min_score="" /> --> <!-- The storage device the quorum daemon uses. The device must be the same on all nodes. It has no default and must be set unless you set 'label' below. For example, if you created your quorum disk with the call: mkqdisk -c /dev/sdi1 -l rac_qdisk This will be set to '/dev/sdi1'. When possible, use set the 'label' option below as it is more robust. If you use 'label' instead of this then the device does *not* need to be the same amoung nodes. In short, don't set this unless you have a good reason to. Q. Is this true? --> <!-- <quorumd device="" /> --> <!-- Specifies the quorum disk label created by the 'mkqdisk' utility. If you look at the example given in the 'device' argument above, then this would be 'rac_qdisk'. Setting this instead of 'device' is preferable. If you set this, then 'device' is in fact ignored. If this field is used, the quorum daemon reads '/proc/partitions' and checks for qdisk signatures on every block device found, comparing the label against the value below. This is useful in configurations where the quorum device name differs among nodes. --> <!-- <quorumd label="" /> --> <!-- DLM; The Distributed Lock Manager --> <!-- Options must be combined in one <dlm... /> statement. --> <!-- This tells DLM to use automatically determine whether to use TCP or SCTP depending on the 'rrp_mode'. You can force one protocol by setting this to 'tcp' or 'sctp'. If 'rrp_mode' is 'none', then 'tcp' is used. The default is 'detect'. --> <!-- <dlm protocol="detect" /> --> <!-- This specifies how many 100ths of a second (centiseconds) to wait before dlm emits a warning via netlink. This value is used for deadlock detection and only applies to lockspaces created with the DLM_LSFL_TIMEWARN flag. The default is 5 seconds ('500'). --> <!-- <dlm timewarn="500" /> --> <!-- Setting this to '1' will enable DLM debug messages. The default is '0' (disabled). Q: Do these messages go to /var/log/messages ? --> <!-- <dlm log_debug="0" /> --> <!-- DLM daemon options --> <!-- This controls fencing recovery dependency. The default is enabled, '1'. Set this to '0' to disable fencing dependency. Q. Does this allow cman to start when no fence device is configured? --> <!-- <dlm enable_fencing="1" /> --> <!-- This controls quorum recovery dependency. The default is enabled, '1'. Set this to '0' to disable quorum dependency. Q. Does this mean that a non-quorum partition will attempt to continue functioning? --> <!-- <dlm enable_quorum="0" /> --> <!-- The controls the deadlock detection code. The default is '1', to enable deadlock detection. Set this to '0' to disable it. The default is '0', disabled. Q. Is this primarily a debugging tool? --> <!-- <dlm enable_deadlk="0" /> --> <!-- This controls the posix lock code for clustered file systems. This is required by cluster-aware filesystems like GFS2, OCFS2 and similar. In some cases though, like Oracle RAC, plock is implemented internally and thus needs to be disabled in the cluster. Also, plock can be expensive in terms of latency and bandwidth. Disabling this may help improve performance but should only be done if you are sure you do not need posix locking in your cluster. The default is '1', enabled. To disable it, set this to '0'. Unlike 'flock' (file lock), which locks an entire file, plock allows for locking parts of a file. When a plock is set, the filesystem must know the start and length of the lock. In clustering, this information is sent between the nodes via cpg (the cluster process group), which is a small process layer on top of the totem protocol in corosync. Messages are of the form 'take lock (pid, inode, start, length)'. Delivery of these messages are kept in the same order on all nodes (total order), which is a property of 'virtual synchrony'. For example, if you have three nodes; A, B and C, and each node sends two messages, cpg ensures that the message all arrive in the same order across all nodes. For example, the messages may arrive as 'c1,a1,a2,b1,b2,c2'. The actual order doesn't matter though. For more information on posix locks, see the 'fcntl' man page and read the sections on 'F_SETLK' and 'F_GETLK'. For more information on cpg, install the corosync development libraries (corosynclib-devel) and then read the 'cpg_overview' man page. --> <!-- <dlm enable_plock="1" /> --> <!-- This controls the rate of plock operations per second. The default is '0', which is "unlimited". Set a positive whole integer to impose a limit. This mat be needed is excessive plock messages are causing network load issues. --> <!-- <dlm plock_rate_limit="0"/> --> <!-- This controls the plock ownership function. When enabled, performance gains may be seen where a given node repeatedly issues the same lock. By default, this is set to '1', enabled. This can affect backward compatibility with older versions of dlm. To disable it, set this to '0'. Q. Is this right? This should be explained better. --> <!-- <dlm plock_ownership="1" /> --> <!-- This is the number of milliseconds to wait before dropping the cache of lock information. The default is 10 seconds (10000). The lower this value, the better the performance but the more memory will be used. NOTE: This value is ignored when 'plock_ownership' is disabled. Q. Is this right? --> <!-- <dlm drop_resources_time="10000" /> --> <!-- This is the number of cached items to attempt to drop each 'drop_resources_time' milliseconds. The higher this number, the better the potential performance, but the more memory will be used. NOTE: This value is ignored when 'plock_ownership' is disabled. Q. Is this right? --> <!-- <dlm drop_resources_count="10" /> --> <!-- This is the number of milliseconds that a cached item is allowed to go unused before it is set to be dropped. The default it 10 seconds (10000). The lower this value, the better the performance but the more memory will be used. NOTE: This value is ignored when 'plock_ownership' is disabled. Q. Is this right? --> <!-- <dlm drop_resources_age="10000" /> --> <!-- All default DLM options listed below. --> <dlm protocol="detect" timewarn="500" log_debug="0" enable_fencing="1" enable_quorum="0" enable_deadlk="0" enable_plock="1" plock_rate_limit="0" plock_ownership="1" drop_resources_time="10000" drop_resources_count="10" drop_resources_age="10000" /> <!-- GFS Control daemon --> <!-- There are several <gfs_controld...> arguments that are still supported, but they have been deprecated in favour of the <dlm_controld...> arguments. To see a full list, please read the 'gfs_controld(8)' man page. The one remaining argument that is still current is 'enable_withdraw'. When set to '1', the default, GFS will respond to a withdrawl. To disable the responce, set this to '0'. Q. What does the responce actually do? --> <gfs_controld enable_withdraw="1"/> <!-- Cluster Nodes --> <clusternodes> <!-- AN!Cluster Node 1 --> <!-- The clusternode 'name' value must match the name returned by `uname -n`. The network interface with the IP address mapped to this name will be the network used by the totem ring. The totem ring is used for cluster communication and reconfiguration, so all nodes must use network interfaces on the same network for the cluster to form. For the same reason, this name must not resolve to the localhost IP address (127.0.0.1/::1). Optional <clusternode ...> arguments: - weight="#"; This sets the DLM lock directory weight. This is a DLM kernel option. Q. This needs better explaining. --> <clusternode name="an-node01.alteeve.com" nodeid="1"> <!-- By default, an initial totem ring will be created on the interface that maps to the name above. Under Corosync, this would have been "ring 0". To set up a second totem ring. The 'name' must be resolvable to an IP address on the network card you want you second ring on. Further, all other nodes must be setup to use the same network as their second ring as well. NOTE: Currently broken, do not use until this warning NOTE: has been removed. --> <!-- <altname name="an-node01-sn" port="6899" mcast="188.8.131.52" /> --> <!-- Fence Devices attached to this node. --> <fence> <!-- The entries here reference devices defined below in the <fencedevices/> section. The options passed control how the device is called. When multiple devices are listed, they are tried in the order that the are listed here. The 'name' argument must match a 'name' argument in the '<fencedevice>' section below. The details must define how 'fenced' will fence *this* device. The 'method' name seems to be unpassed to the fence agent and is useful to the human reader only? All options here are passed as 'var=val' to the fence agent, one per line. Note that 'action' was formerly known as 'option'. In the 'fence_na' agent, 'option' will be converted to 'action' if used. --> <method name="node_assassin"> <device name="batou" port="01" action="reboot"/> </method> </fence> </clusternode> <!-- AN!Cluster Node 2 --> <clusternode name="an-node02.alteeve.com" nodeid="2"> <altname name="an-node02-sn" port="6899" mcast="184.108.40.206" /> <fence> <method name="node_assassin"> <device name="batou" port="02" action="reboot"/> </method> </fence> </clusternode> </clusternodes> <!-- The fence device is mandatory and it defined how the cluster will handle nodes that have dropped out of communication. In our case, we will use the Node Assassin fence device. --> <fencedevices> <!-- This names the device, the agent (script) to controls it, where to find it and how to access it. --> <fencedevice name="batou" agent="fence_na" ipaddr="batou.alteeve.com" login="section9" passwd="project2501" quiet="1"></fencedevice> <fencedevice name="motoko" agent="fence_na" ipaddr="motoko.alteeve.com" login="section9" passwd="project2501" quiet="1"></fencedevice> <!-- If you have two or more fence devices, you can add the extra one(s) below. The cluster will attempt to fence a bad node using these devices in the order that they appear. --> </fencedevices> <!-- When the cluster starts, any nodes not yet in the cluster may be fenced. By default, there is a 6 second buffer, but this isn't very much time. The following argument increases the time window where other nodes can join before being fenced. I like to give up to one minute but the Red Hat man page suggests 20 seconds. Please do your own testing to determine what time is needed for your environment. --> <fence_daemon post_join_delay="60"> </fence_daemon> </cluster>
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