Managing NFS and KRPC Kernel Configurations in HP-UX 11i v3 (762807-001, March 2014)

server returns as well as the maximum size of the request the client generates over a connection-
oriented transport, such as TCP.
The nfs4_max_transfer_size_cots tunable works in conjunction with the nfs4_bsize and
nfs4_max_transfer_size tunables when determining the maximum size of these I/O requests. For
NFSv4 TCP traffic, the transfer size corresponds to the smallest value of nfs4_bsize,
nfs4_max_transfer_size, and nfs4_max_transfer_size_cots.
The nfs3_max_transfer_size_cots tunable specifies the maximum size of the data portion of NFSv3
requests. For more information on the tunable, see nfs3_max_transfer_size_cots.
Tested Values
Default: 1048576
Min: 4096
Max: 1048576
Note: If the tunable is set to a value greater than 1048576,
an informational warning is issued at runtime. Any value
greater than 1048576 is outside the tested limits.
Restrictions on Changing
The nfs4_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, the system administrator must unmount and re-
mount the filesystem after changing this tunable. Only NFSv4 mount points are affected by changing
the value of this tunable.
Modifying the Value
For NFS/TCP Filesystems:
To increase the transfer size of NFSv4 TCP requests, set the nfs4_bsize, nfs4_max_transfer_size, and
nfs4_max_transfer_size_cots tunables to the same value. Otherwise, the transfer size will default to the
smallest value of these three tunables. For example, if 1 MB transfers are desired, all three tunables
must be set to at least 1 MB. If two of the tunables are set to 1 MB and the third is set to 32 KB, the
transfer size will be 32 KB since that is the smallest value of the three tunables.
To decrease the size of NFSv4 TCP requests, decrease the value of the nfs4_max_transfer_size_cots
tunable. For example, to decrease the size of I/O requests on all NFSv4 TCP filesystems to 8 KB, set
the value of nfs4_max_transfer_size_cots to 8192.
Caution: If the NFS client is experiencing NFS READ failures
and the system is reporting "NFS read failed for server
<servername>: RPC: Can’t decode result" errors, this is an
indication that the nfs4_bsize, nfs4_max_transfer_size, or
nfs4_max_transfer_size_cots tunable value was changed
while NFS filesystems were mounted. The system