A cluster file system (CFS) is a file system that may be accessed (read and write) by all members in a cluster at the same time. This implies that all members of a cluster have the same view.If your platform supports an Oracle certified cluster file system, you can store the files that Real Application Clusters requires directly on the cluster file system.
A clustered file system is a file system which is simultaneously mounted on multiple servers. There are several approaches to clustering, most of which do not employ a clustered file system. While many computer clusters don't use clustered file systems, unless servers are underpinned by a clustered file system the complexity of the underlying storage environment increases as servers are added.
Distributed file system - the generic term for a client/server or "network" file system where the data isn't locally attached to a host.
Global file system - this refers to the namespace, so that all files have the same name and path name when viewed from all hosts. This obviously makes it easy to share data across machines and users in different parts of the organization.
OCFS2 (Oracle Cluster File System 2) is a free, open source, general-purpose, extent-based clustered file system which Oracle developed and contributed to the Linux community, and accepted into Linux kernel 2.6.16.
OCFS2 provides an open source, enterprise-class alternative to proprietary cluster file systems, and provides both high performance and high availability. OCFS2 provides local file system semantics and it can be used with any application. Cluster-aware applications can leverage parallel I/O for higher performance, and other applications can make use of the file system to provide a fail-over setup to increase availability.
Cluster file system - a distributed file system that is not a single server with a set of clients, but instead a cluster of servers that all work together to provide high performance service to their clients. To the clients the cluster is transparent - it is just "the file system", but the file system software deals with distributing requests to elements of the storage cluster.
Shared-disk cluster file system
The most common type of clustered file system is the shared disk file system, in which two or more servers are connected to a single shared storage subsystem, such as a stand-alone RAID array or SAN.
Symmetric file system - A symmetric file system is one in which the clients also run the metadata manager code; that is, all nodes understand the disk structures.
Asymmetric file system - An asymmetric file system is one in which there are one or more dedicated metadata managers that maintain the file system and its associated disk structures.
Shared-nothing clustered file system
Another clustered file system approach is to have each node use its own local storage, and communicate data changes to other nodes via some network or bus. In this case disks are not shared amongst nodes, but are instead dedicated to a single node and made readable and writable to other servers
Parallel file system - file systems with support for parallel applications, all nodes may be accessing the same files at the same time, concurrently reading and writing. Data for a single file is striped across multiple storage nodes to provide scalable performance to individual files.
SAN file system - These provide a way for hosts to share Fibre Channel storage, which is traditionally carved into private chunks bound to different hosts. To provide sharing, a block-level metadata manager controls access to different SAN devices. A SAN File system mounts storage natively in only one node, but connects all nodes to that storage and distributes block addresses to other nodes. Scalability is often an issue because blocks are a low-level way to share data placing a big burden on the metadata managers and requiring large network transactions in order to access data.
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