Which two statements about Oracle Direct Network File System (NFS) are true? (Choose
two.)
A.
It bypasses the OS file system cache.
B.
A separate NFS interface is required for use across Linux, UNIX, and Windows platforms.
C.
It uses the operating system kernel NFS layer for user tasks and network communication
modules.
D.
File systems need not be mounted by the kernel NFS system when being served through
Direct NFS.
E.
Oracle Disk Manager can manage NFS on its own, without using the operating system
kernel NFS driver.
Explanation:
Direct NFS provides faster performance that what can be provided by the operating system’s
NFS driver as Oracle bypasses the operating system and generates exactly the requests it
needs (no user configuration or tuning required). Data is cached just once in user space,
which saves memory (no second copy in kernel space). Performance is further improved by
load balancing across multiple network interfaces (if available).
A and E are correct:
http://www.oracle.com/technetwork/articles/directnfsclient-11gr1-twp-129785.pdf
A: First, Direct NFS Client is capable of performing concurrent
direct I/O, which bypasses any operating system level caches and eliminates any
operating system write-ordering locks.
E: Client systems use
the operating system provided NFS driver to facilitate the communication between the
client and the NFS server. While this approach has been successful, drawbacks such as
performance degradation and complex configuration requirements have limited the
benefits of using NFS and NAS for database storage.
Oracle Database 11g Direct NFS Client integrates the NFS client functionality directly
in the Oracle software. Through this integration, Oracle is able to optimize the I/O
path between Oracle and the NFS server providing significantly superior performance.
In addition, Direct NFS Client simplifies, and in many cases automates, the
performance optimization of the NFS client configuration for database workloads.
DIRECT NFS CLIENT OVERVIEW
Standard NFS client software, provided by the operating system, is not optimized for
Oracle Database file I/O access patterns. With Oracle Database 11g, you can configure
Oracle Database to access NFS V3 NAS devices directly using Oracle Direct NFS
Client, rather than using the operating system kernel NFS client. Oracle Database will
access files stored on the NFS server directly through the integrated Direct NFS Client
eliminating the overhead imposed by the operating system kernel NFS. These files are
also accessible via the operating system kernel NFS client thereby allowing seamless
administration.