When To Use CFS

Technical Overview

Benefits and Applications

You should use CFS for any application that requires file sharing, such as for home directories, web pages, and for cluster-ready applications. CFS can also be used when you want highly available standby data in predominantly read-only environments, or when you do not want to rely on NFS for file sharing.

Almost all applications can benefit from CFS. Applications that are not “cluster-aware” can operate and access data from anywhere in a cluster. If multiple cluster applications running on different servers are accessing data in a cluster file system, overall system I/O performance improves due to the load balancing effect of having one cluster file system on a separate underlying volume. This is automatic; no tuning or other administrative action is required.

Many applications consist of multiple concurrent threads of execution that could run on different servers if they had a way to coordinate their data accesses. CFS provides this coordination. These applications can be made cluster-aware allowing their instances to co-operate to balance the client and data access load, and thereby scale beyond the capacity of any single server. In these applications, CFS provides shared data access, enabling application-level load balancing across cluster nodes.

•For single-host applications that must be continuously available, CFS can reduce application failover time, because it provides an already-running file system environment in which an application can restart after a server failure.

•For parallel applications, such as distributed database management systems and web servers, CFS provides shared data to all application instances concurrently. CFS also allows these applications to grow by the addition of servers, and improves their availability by enabling them to redistribute load in the event of server failure simply by reassigning network addresses.

•For workflow applications, such as video production, in which very large files are passed from station to station, CFS eliminates time consuming and error prone data copying by making files available at all stations.

•For backup, CFS can reduce the impact on operations by running on a separate server, while accessing data in cluster-shareable file systems.

Some common applications for CFS are:

•Using CFS on file servers

Two or more servers connected in a cluster configuration (that is, connected to the same clients and the same storage) serve separate file systems. If one of the servers fails, the other recognizes the failure, recovers, assumes the role of primary node, and begins responding to clients using the failed server’s IP addresses.

•Using CFS on web servers

Web servers are particularly suitable to shared clustering, because their application is typically read-only. Moreover, with a client load balancing front end, a Web server cluster’s capacity can be expanded by adding a server and another copy of the site. A CFS-based cluster greatly simplifies scaling and administration for this type of application.

Chapter 1