Veritas Storage Foundation 5.0 for Oracle RAC Configuration Guide Extracts for HP Serviceguard Storage Management Suite, Second Edition, May 2008

Planning SGeRAC Installation and Configuration
About CVM and CFS in an SGeRAC Environment
Chapter 2
31
About CFS
Review CFS File System benefits, CFS configuration differences from VxFS and CFS
recovery operations.
CFS File System Benefits
Many features available in VxFS do not come into play in an SGeRAC environment
because ODM handles such features. CFS adds such features as high availability,
consistency and scalability, and centralized management to VxFS. Using CFS in an
SGeRAC environment provides the following benefits:
• Increased manageability, including easy creation and expansion of files
Without a file system, you must provide Oracle with fixed-size partitions. With CFS,
you can grow file systems dynamically to meet future requirements.
• Less prone to user error
Raw partitions are not visible and administrators cannot compromise them by
mistakenly putting file systems over the partitions. Nothing exists in Oracle to
prevent you from making such a mistake.
• Data center consistency
If you have raw partitions, you are limited to a RAC-specific backup strategy. CFS
enables you to implement your backup strategy across the data center.
CFS Configuration Differences
The first node to mount a CFS file system as shared becomes the primary node for that
file system. All other nodes are “secondaries” for that file system.
Use the fsclustadm command from any node to view which node is primary and set the
CFS primary node for a specific file system.
Mount the cluster file system individually from each node. The -o cluster option of the
mount command mounts the file system in shared mode, which means you can mount the
file system simultaneously on mount points on multiple nodes.
When using the fsadm utility for online administration functions on VxFS file systems,
including file system resizing, defragmentation, directory reorganization, and querying
or changing the largefiles flag, run fsadm from the primary node. This command fails
from secondaries.
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.