Managing NFS and KRPC Kernel Configurations in HP-UX 11i v2 (November 2013)

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Note: The nfs3_max_transfer_size_clts tunable affects every
NFSv3 filesystem. To control the transfer sizes of specific
NFS filesystems, use the rsize and wsize mount options.
Refer to the mount_nfs(1M) manpage for more information.
2.1.22 nfs3_max_transfer_size_cots
Description
The nfs3_max_transfer_size_cots tunable specifies the maximum size of the data portion of NFSv3
READ, WRITE, READDIR, and READDIRPLUS requests. This parameter controls both the maximum size
of the data the server returns and the maximum size of the request the client generates over a
connection-oriented transport, such as TCP.
The nfs3_max_transfer_size_cots tunable works in conjunction with the nfs3_max_transfer_size
tunable when determining the maximum size of these I/O requests. For NFSv3 TCP traffic, the transfer
size corresponds to the smaller value of nfs3_max_transfer_size and nfs3_max_transfer_size_cots.
Tested values
Default: 32768
Min: 4096
Max: 65536
Note: If the tunable is set to a value less than 4096 or
greater than 65536, an informational warning is issued at
runtime. These values are outside the tested limits.
Restrictions on changing
The nfs3_max_transfer_size_cots tunable is dynamic. System reboot is not required to activate
changes made to this tunable. However, the transfer size for a filesystem is set when the filesystem is
mounted. In order to affect a particular filesystem, you must unmount and re-mount the filesystem after
changing this tunable. Only NFSv3 mount points are affected by changing the value of this tunable.
Modifying the value
For NFS/TCP Filesystems:
To increase the transfer size of NFSv3 TCP requests, set the nfs3_max_transfer_size and
nfs3_max_transfer_size_cots tunables to the same value. Otherwise, the transfer size will default to the
smaller value of these two tunables. For example, if 64 KB transfers are desired, both tunables must
be set to at least 64 KB. If one of the tunables is set to 64 KB and the other is set to 32 KB, the
transfer size is 32 KB because that is the smaller value of the two tunables.
To decrease the size of NFSv3 TCP requests, decrease the value of the nfs3_max_transfer_size_cots
tunable. For example, to decrease the size of I/O requests on all NFSv3 TCP filesystems to 8 KB, set
the value of nfs3_max_transfer_size_cots to 8192.