Go Oracle 11g Direct NFS

Direct NFS Client
NAS storage devices Use the Network File System (NFS) to access data. In Oracle Database 10g, NAS devices were accessed using operating system–specific kernel NFS drivers. This required, tune many parameters, and the configuration varied across the platforms. The NFS clients tended to be inconsistent across the different operating system platforms. Manageability wasn ' t easy because your had to contend with over configuration parameters.
In Oracle Database 11g, the Oracle NFS implements the NFS Version 3 protocol in the Oracle RDBMS kernel. Implementing the Oracle Direct NFS offers the following benefits:
Avoids the bottlenecks and resource constraints by avoiding the kernel NFS layer.
Provides a common NFS interface for Oracle for use with all operating system platforms and supported NFS servers.
Provides load balancing across multiple connections to the NFS servers, thus improving performance.
Performance is predictable because the Oracle NFS implementation enables your to completely control the Input/output path T o the Network File Servers.
Easier management including simpler configuration and superior diagnosability.
Configuring Direct NFS
You do not have the configure much to implement Oracle Direct NFS Client. Direct NFS searches for the mount point entries in the following order:
$ORCLE _home/dbs/oranfstab
/etc/orafnstab
/etc/mtab
The database uses the first match as the mount point. Oracle always requires this even when you use Direct NFS, the kernel NFS system must perform the mounting. For this reason, Oracle would always crosscheck the information about mount points in the Oranfstab file with the operating System NFS mount points. If there ' s a mismatch, Direct NFS can ' t act as a client to the NFS server and stops serving the NFS server.
enabling Direct NFS
You must follow these steps to enable Direct NFS:
1.You must mount all NFS mount points with your kernel NFS client. You must make sure your mount any file systems you plan on using through ODM NFS and make the file systems available to Ora CLE over regular NFS mounts.
2.If want to specify oracle-specific options to Direct NFS, you'll need an oranfstab file. This was an optional step. The Oranfstab file must has the following attributes so the database can access all NFS servers through Direct NFS:
Server:provides the NFS server name.
Mount:provides The local mount point for the NFS server.
Export:provides the exported path from the NFS server.
Path:provides the network path to the NFS server. You can specify-to-four network paths with a IP address or by name. Using The multiple network paths enables the Direct NFS client to use the a alternate path if the current path fails. Multiple paths also enable the client to perform load balancing.
Mnt_timeout:specifies (in seconds), the time Direct NFS Client should wait for a successful mount before timing out. This parameter is optional. The default timeout is minutes (600).
Dontroute:specifies that outgoing messages should is routed by the operating system, but instead sent using the IP ad Dress to which they is bound. Note that this POSIX option sometimes does is on Linux systems with multiple paths in the same subnet.
A typical Oranfstab file looks similar to the following:
Server:testserver1
path:130.33.34.11
Export:/vol/oradata1
Mount:/mnt/oradata1
In order to remove a NFS path that the database was using currently, you must restart the database.
3. You must replace the "standard" ODM library, libnfsodm10.so, with the ODM for NFS Library, as shown here:
$ cd $ORACLE _home/lib
$ cp libodmll.so libodmll.so_stub
$ ln-s libnfsodm11.so libodm11.so
You can disable the Direct NFS client by using any of the following three methods.
Delete the Oranfstab file.
Replace the ODM NFS library with the stub libodm11.so file.
Modify the Oranfstab file by deleting the specific NFS server or the network paths to the NFS server.
If the database can ' t open the NFS server using Direct NFS, it'll use the operating system kernel client instead.
Monitoring Direct NFS
You can query the following views in order to manage Direct NFS:
V$dnfs_stats shows performance statistics for Direct NFS.
V$dnfs_servers shows SERVERS accessed by Direct NFS.
V$dnfs_files shows FILES currently using Direct NFS.
V$dnfs_channels shows the open network paths being used by Direct NFS.

Reference to: "mcgraw.hill.ocp.oracle.database.11g.new.features.for.administrators.exam.guide.apr.2008"
http://docs.oracle.com/cd/E11882_01/install.112/e41961/storage.htm#CWLIN279

http://czmmiao.iteye.com/blog/1965839