Veritas Storage Foundation 5.0.1 Cluster File System Administrator's Guide Extracts for the HP Serviceguard Storage Management Suite on HP-UX 11i v3

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.
Benefits and Applications 13