Veritas Storage Foundation 5.1 SP1 for Oracle RAC Administrator"s Guide (5900-1512, April 2011)

CFS recovery

The vxfsckd daemon is responsible for ensuring file system consistency when a

node crashes that was a primary node for a shared file system. If the local node

is a secondary node for a given file system and a reconfiguration occurs in which

this node becomes the primary node, the kernel requests vxfsckd on the new

primary node to initiate a replay of the intent log of the underlying volume. The

vxfsckd daemon forks a special call to fsck that ignores the volume reservation

protection normally respected by fsck and other VxFS utilities. The vxfsckd can

check several volumes at once if the node takes on the primary role for multiple

file systems.

After a secondary node crash, no action is required to recover file system integrity.

As with any crash on a file system, internal consistency of application data for

applications running at the time of the crash is the responsibility of the

applications.

Comparing raw volumes and CFS for data files

Keep these points in mind about raw volumes and CFS for data files:

■ If you use file-system-based data files, the file systems containing these files

must be located on shared disks. Create the same file system mount point on

each node.

■ If you use raw devices, such as VxVM volumes, set the permissions for the

volumes to be owned permanently by the database account.

VxVM sets volume permissions on import. The VxVM volume, and any file

system that is created in it, must be owned by the Oracle database user.

Oracle Disk Manager

SF Oracle RAC requires Oracle Disk Manager (ODM), a standard API published by

Oracle for support of database I/O. SF Oracle RAC provides a library for Oracle to

use as its I/O library.

ODM architecture

When the Veritas ODM library is linked, Oracle is able to bypass all caching and

locks at the file system layer and to communicate directly with raw volumes. The

SF Oracle RAC implementation of ODM generates performance equivalent to

performance with raw devices while the storage uses easy-to-manage file systems.

All ODM features can operate in a cluster environment. Nodes communicate with

each other before performing any operation that could potentially affect another

Overview of Veritas Storage Foundation for Oracle RAC

Component products and processes of SF Oracle RAC