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       o2cb - Default cluster stack for the OCFS2 file system.


       o2cb  is  the  default cluster stack for the OCFS2 file system. It includes a node manager
       (o2nm) to keep track of the nodes in the cluster, a heartbeat agent (o2hb) to detect  live
       nodes, a network agent (o2net) for intra-cluster node communication and a distributed lock
       manager (o2dlm) to keep track of lock resources. All these components  are  in-kernel.  It
       also  includes an in-memory file system, dlmfs, to allow userspace to access the in-kernel

       This cluster stack  has  two  configuration  files,  namely,  /etc/ocfs2/cluster.conf  and
       /etc/sysconfig/o2cb.  Whereas  the  former  keeps  track of the cluster layout, the latter
       keeps track of the cluster timeouts. Both files are only read when the cluster is  brought
       online.    Values   in   use   by   the   online   cluster   can   be   perused   in   the
       /sys/kernel/config/cluster directory structure.


       The cluster layout is specified in /etc/ocfs2/cluster.conf. While it is easier to populate
       and  propagate  this  configuration  file  using  ocfs2console(8),  one  can also do it by
       manually as long as care is taken to format the file correctly.

       While the console utility is intuitive to use, there are few points to keep in mind.

            1. The node name needs to match the hostname. It does not need to include the  domain
       name. For example, can be appserver.

            2. The IP address need not be the one associated with that hostname. As in, any valid
       IP address on that node can be used.  O2CB  will  not  attempt  to  match  the  node  name
       (hostname) with the specified IP address.

       For best performance, use of a private interconnect (lower latency) is recommended.

       The cluster.conf file is in a stanza format with two types of stanzas, namely, cluster and
       node. A typical cluster.conf will have one cluster stanza and multiple node stanzas.

       The cluster stanza has two parameters:

              Total number of nodes in the cluster

       name   Name of the cluster

       The node stanza has five parameters:

              IP port

              IP address

       number Unique node number from 0-254

       name   Hostname

              Name of the cluster

       Users populating cluster.conf manually should follow the format strictly.  As  in,  stanza
       header  should  start  at  the first column and end with a colon, stanza parameters should
       start after a tab, a blank line should demarcate each stanza and care taken to avoid stray

       The O2CB cluster timeouts are specified in /etc/sysconfig/o2cb and can be configured using
       the o2cb init script.

       These timeouts are used by the O2CB clusterstack to determine whether a node  is  dead  or
       alive.  While  the  use  of default values is recommended, users can experiment with other
       values if the defaults are causing spurious fencing.

       The cluster timeouts are:

       Heartbeat Dead Threshold
              The Disk Heartbeat timeout is the number of two second iterations before a node  is
              considered  dead.  The  exact formula used to convert the timeout in seconds to the
              number of iterations is as follows:

              O2CB_HEARTBEAT_THRESHOLD = (((timeout in seconds) / 2) + 1)

              For e.g., to specify a 60 sec timeout, set it to 31. For 120 secs, set  it  to  61.
              The default for this timeout is 60 secs (O2CB_HEARTBEAT_THRESHOLD = 31).

       Network Idle Timeout
              The  Network  Idle  timeout  specifies  the  time  in milliseconds before a network
              connection is considered dead. It defaults to 30000 ms.

       Network Keepalive Delay
              The Network  Keepalive  specifies  the  maximum  delay  in  milliseconds  before  a
              keepalive  packet  is  sent to another node to check whether it is alive or not. If
              the node is alive, it will respond. Its defaults to 2000 ms.

       Network Reconnect Delay
              The  Network  Reconnect  specifies  the  minimum  delay  in  milliseconds   between
              connection attempts. It defaults to 2000 ms.


       A sample /etc/ocfs2/cluster.conf.

           node_count = 3
           name = webcluster

           ip_port = 7777
           ip_address =
           number = 7
           name = node7
           cluster = webcluster

           ip_port = 7777
           ip_address =
           number = 6
           name = node6
           cluster = webcluster

           ip_port = 7777
           ip_address =
           number = 10
           name = node10
           cluster = webcluster


       mkfs.ocfs2(8) fsck.ocfs2(8) tunefs.ocfs2(8) debugfs.ocfs2(8) ocfs2console(8)


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