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
Table 1-2 CFS Unsupported Features (continued)
Features and Commands Not Supported on CFS
File access times may appear different across nodes because the atime file attribute is not
closely synchronized in a cluster file system. Utilities that depend on checking access times
may not function reliably.
Commands that
Depend on File Access
Times
HP Serviceguard does not support CFS nested mounts.Nested Mounts
Benefits and Applications
The following sections describe CFS benefits and some applications.
Advantages To Using CFS
CFS simplifies or eliminates system administration tasks resulting from hardware limitations:
• The CFS single file system image administrative model simplifies administration by allowing
all file system management operations, resizing, and reorganization (defragmentation) to
be performed from any node.
• You can create and manage terabyte-sized volumes, so partitioning file systems to fit within
disk limitations is usually not necessary - only extremely large data farms must be partitioned
to accommodate file system addressing limitations. For maximum supported file system
sizes, see Supported File and File System Sizes for HFS and JFS available at: http://
docs.hp.com/en/oshpux11iv3.html#VxFS
• Keeping data consistent across multiple servers is automatic, because all servers in a CFS
cluster have access to cluster-shareable file systems. All cluster nodes have access to the
same data, and all data is accessible by all servers using single server file system semantics.
• Applications can be allocated to different servers to balance the load or to meet other
operational requirements, because all files can be accessed by all servers. Similarly, failover
becomes more flexible, because it is not constrained by data accessibility.
• The file system recovery portion of failover time in an n-node cluster can be reduced by a
factor of n, by distributing the file systems uniformly across cluster nodes, because each CFS
file system can be on any node in the cluster.
• Enterprise storage arrays are more effective, because all of the storage capacity can be
accessed by all nodes in the cluster, but it can be managed from one source.
• Larger volumes with wider striping improve application I/O load balancing. Not only is the
I/O load of each server spread across storage resources, but with CFS shared file systems,
the loads of all servers are balanced against each other.
• Extending clusters by adding servers is easier because each new server’s storage configuration
does not need to be set up - new servers simply adopt the cluster-wide volume and file
system configuration.
• For the following HP Serviceguard Storage Management Suite CFS for Oracle bundles, the
clusterized Oracle Disk Manager (ODM) feature is available to applications running in a
cluster, enabling file-based database performance to approach the performance of raw
partition-based databases:
— T2777DB, T8686DB, T8687DB, T8696DB, and T8697DB
When To Use CFS
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
12 Technical Overview