nfs3_max_transfer_size_cots.5 (2010 09)

n
nfs3_max_transfer_size_cots(5) nfs3_max_transfer_size_cots(5)
(Tunable Kernel Parameters)
NAME
nfs3_max_transfer_size_cots - controls the data portion size of a NFS version 3 read, write, readdir, or
readdirplus request over TCP
VALUES
Failsafe
1048576
Default
1048576
Allowed values
Minimum: 4096
Maximum: MAXINT
Recommended values
A warning will be issued at runtime if the tunable is set to a value greater than 1048576 since this is out-
side the tested limits. This is not a serious warning but just an information message for the administra-
tor.
DESCRIPTION
nfs3_max_transfer_size_cots
controls the maximum size of the data portion of a NFS version 3
read, write, readdir, or readdirplus request over TCP. This parameter controls both the maximum size of
a request that the server returns as well as the maximum size of a request that the client generates.
Who Is Expected to Change This Tunable?
Distributed file system administrators should examine this value if they want to decrease or increase the
default size of a NFS version 3 packet over TCP.
Restrictions on Changing
The
nfs3_max_transfer_size_cots
tunable is dynamic; however, the transfer size for a file sys-
tem is set when the file system is mounted. To affect a particular file system, unmount and mount the file
system after changing this parameter.
The actual NFS version 3 transfer size over TCP is controlled by these tunable parameters:
nfs3_bsize, nfs3_max_transfer_size
, and nfs3_max_transfer_size_cots
. The actual
transfer size will depend on the tunable with the smallest value. For NFS TCP traffic increase
nfs3_max_transfer_size
, nfs3_max_transfer_size_cots, and
nfs3_bsize to the same
value to increase the transfer size. To decrease the transfer size, just changing
nfs3_bsize is sufficient.
When Should the Value of This Tunable Be Raised?
An increase in the transfer size will result in fewer requests to the NFS server at the expense of system
resources on both the NFS client and NFS server.
What Are the Side Effects of Raising the Value?
Setting the limit large causes more system resources to be consumed by both the NFS client and NFS
server.
When Should the Value of This Tunable Be Lowered?
In the event of NFS communication failures, the value should be changed back to the default value.
What Are the Side Effects of Lowering the Value?
An increase in NFS version 3 network traffic over TCP caused by an increase in the number of I/O
requests.
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
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1