NAME
nfs4_max_transfer_size_cots — control the data portion size of a NFS version 4 read, write, readdir, or readdirplus request over TCP
VALUES
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 outside the tested limits.
This is not a serious warning but
just an information message for the administrator.
DESCRIPTION
nfs4_max_transfer_size_cots
controls the maximum size of the data portion of a NFS version 4 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 4
packet over TCP.
Restrictions on Changing
The
nfs4_max_transfer_size_cots
tunable is dynamic; however, the transfer size for a file system 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 4 transfer size over TCP is controlled by these
tunable parameters:
nfs4_bsize,
nfs4_max_transfer_size,
and
nfs4_max_transfer_size_cots.
The actual transfer size will depend on the tune with the smallest
value. For NFS TCP traffic you should increase
nfs4_max_transfer_size,
nfs4_max_transfer_size_cots,
and
nfs4_bsize
to the same value to increase the transfer size. To decrease the
transfer size, just changing
nfs4_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 4 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 parameter 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://docs.hp.com.
AUTHOR
nfs4_max_transfer_size
was developed by Sun Microsystems, Inc.
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