Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual page 495

25.2.6 Oracle Cluster File System 2
OCFS2 is a journaling file system that has been tailor-made for clustering setups. In
contrast to a standard single-node file system like Ext3, OCFS2 is capable of managing
several nodes. OCFS2 allows spreading a file system across shared storage, such as a
SAN or multipath setup.
Every node in an OCFS2 setup has concurrent read and write access to all data. This
requires OCFS2 to be cluster-aware, meaning that OCFS2 must include a means to
determine of which nodes the cluster consists and whether these nodes are actually
alive and available. To compute a cluster's membership, OCFS2 includes a node man-
ager (NM). To monitor the availability of the nodes in a cluster, OCFS2 includes a
simple heartbeat implementation. To avoid chaos arising from various nodes directly
accessing the file system, OCFS2 also contains a lock manager, DLM (distributed lock
manager). Communication between the nodes is handled via a TCP-based messaging
system.
Major features and benefits of OCFS2 include:
• Metadata caching and journaling
• Asynchronous and direct I/O support for database files for improved database per-
formance
• Support for multiple block sizes (where each volume can have a different block
size) up to 4 KB, for a maximum volume size of 16 TB
• Cross-node file data consistency
• Support for up to 255 cluster nodes
For more in-depth information about OCFS2, refer to Chapter 14, Oracle Cluster File
System 2 (page 289).
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