nfs2_nra.5 (2010 09)

n
nfs2_nra(5) nfs2_nra(5)
(Tunable Kernel Parameters)
NAME
nfs2_nra - control the number of read-ahead operations queued by the NFS version 2 client when sequen-
tially accessing a file
VALUES
Failsafe
4
Default
4
Allowed values
Minimum: 0
Maximum: MAXINT
Recommended values
A warning will be issued at runtime if the tunable is set to a value greater than 16 since this is beyond
the tested limit.
This is not a serious warning but just an information message for the administrator.
DESCRIPTION
nfs2_nra controls the number of read-ahead operations that are queued by the NFS version 2 client
when sequential access to a file is discovered. These read-ahead operations increase concurrency and
read throughput. Each read-ahead request is generally for 8192 bytes of file data.
Who Is Expected to Change This Tunable?
The distributed file system administrator should examine this value depending on network bandwidth
and memory pressure on the client.
Restrictions on Changing
The
nfs2_nra tunable is dynamic; tuning will take effect immediately on the running system.
When Should the Value of This Tunable Be Raised?
If the network is very high bandwidth and the client and server have sufficient resources, increase this
value to more effectively utilize the available network bandwidth, the client resources, and the server
resources.
What Are the Side Effects of Raising the Value?
Tuning incorrectly based on network bandwidth can cause performance problems.
When Should the Value of This Tunable Be Lowered?
In a very low bandwidth network, you might want to decrease this value so the NFS client does not over-
load the network.
What Are the Side Effects of Lowering the Value?
Tuning incorrectly based on network bandwidth can cause performance problems.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its
meaning changed in future releases of HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parame-
ter values. After installation, some tunable parameters may no longer be at the default or recommended
values. For information about the effects of installation on tunable values, consult the documentation for
the kernel software being installed. For information about optional kernel software that was factory
installed on your system, see HP-UX Release Notes at
http://www.hp.com/go/hpux-core-docs.
AUTHOR
nfs2_nra was developed by Sun Microsystems, Inc.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1