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
SEE ALSO
mkfs.ocfs2(8) fsck.ocfs2(8) tunefs.ocfs2(8) debugfs.ocfs2(8)
ocfs2console(8)
AUTHORS
Oracle Corporation
COPYRIGHT
Copyright © 2004, 2008 Oracle. All rights reserved.