OCFS2 Integration with HP Serviceguard for Linux Administrator's Guide, Second Edition, May 2009

Figure 2-3 OCFS2 Disk Heartbeat Timeout Definitions

In the figure, t0, t1, t2, t3, and t4 represent the time at which HP Serviceguard for Linux and

OCFS2 realize that there is a disk access failure. Following is the sequence of events:

1. At t0, a node loses connectivity to a storage device because of an FC link failure. This loss

of connectivity immediately halts the I/O from all nodes for a duration which is equal to the

timeout of the I/O layer.

2. At t1, the Disk Monitor Service that monitors the connectivity to disks hangs.

3. At t2, the I/O layer timeout occurs and the Disk Monitor returns with a failure to access the

disk.

4. At t3, Serviceguard ensures that the faulty node is reset, because of the Disk Monitor Service

failure. The faulty node resets and subsequently rejoins the cluster.

5. At t4, the Disk Heartbeat for OCFS2 times out.

IMPORTANT: In this procedure, the Disk Monitor is not the standard Serviceguard Disk Monitor

using cmresserviced. In this integrated environment, do not configure the cmresserviced Disk

Monitor. When you configure the OCFS2 mount point multi-node package using the ocfs2mntadm

administrative utility, the OCFS2 Disk Monitor Service is automatically configured.

In Figure 2-3 (page 21), the time period between t0 and t2 is the timeout of the I/O layer of the

node. Most multi-path solutions have a timeout that ranges from 60 seconds to 120 seconds. This

timeout is determined by the driver that is configured in your environment. The recommended

value of the OCFS2 Disk Heartbeat Timeout is 30 seconds greater than the timeout of the I/O

layer of the node.

Use the following formula to determine the required value for the O2CB_HEARTBEAT_THRESHOLD

parameter:

O2CB_HEARTBEAT_THRESHOLD = (((timeout of the I/O layer <in seconds> +

30 seconds) / 2) + 1)

For example:

If the timeout of the I/O layer is 60 seconds, then according to the formula, the

O2CB_HEARTBEAT_THRESHOLD is 46 seconds.

Pre-configuration Steps 21