Ubuntu Manpage: o2cb - Default cluster stack for the OCFS2 file system.

Provided by: ocfs2-tools_1.6.4-3ubuntu1_amd64

NAME

       o2cb - Default cluster stack for the OCFS2 file system.

DESCRIPTION

       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.

CONFIGURATION

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, appserver.oracle.com 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:

node_count
Total number of nodes in the cluster

name Name of the cluster

The node stanza has five parameters:

ip_port
IP port

ip_address
IP address

number Unique node number from 0-254

name Hostname

cluster
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 ms.

EXAMPLES

       A sample /etc/ocfs2/cluster.conf.

       cluster:
           node_count = 3
           name = webcluster

       node:
           ip_port = 7777
           ip_address = 192.168.0.107
           number = 7
           name = node7
           cluster = webcluster

       node:
           ip_port = 7777
           ip_address = 192.168.0.106
           number = 6
           name = node6
           cluster = webcluster

       node:
           ip_port = 7777
           ip_address = 192.168.0.110
           number = 10
           name = node10
           cluster = webcluster

AUTHORS

       Oracle Corporation

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