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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 dlm.

       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

            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

       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 whitespaces.

       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


       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)


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