VERITAS Storage Foundation 4.1 Cluster File System HP Serviceguard Storage Management Suite Extracts, December 2005

Appendix ,
VxFS Functionality on Cluster File Systems
7
When to Use CFS
You should use CFS for any application that requires the sharing of files, such as for home
directories and boot server files, Web pages, and for cluster-ready applications. CFS is also
applicable when you want highly available standby data, in predominantly read-only
environments where you just need to access data, 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 on and access data from anywhere in a cluster. If multiple cluster unaware
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. Such applications can be made cluster-aware allowing their instances to
co-operate to balance client and data access load, and thereby scale beyond the capacity of
any single server. In such 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, the CFS eliminates time consuming and error prone
data copying by making files available at all stations.
◆ For backup, the CFS can reduce the impact on operations by running on a separate
server, accessing data in cluster-shareable file systems.
The following are examples of applications and how they might work with the CFS: