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

Note: If the tunable is set to a value greater than 1048576
bytes, an informational warning is issued at runtime. Any
value greater than 1048576 is outside the tested limits. The
value of the tunable must be a power of 2.
Restrictions on Changing
The nfs3_bsize tunable is dynamic. System reboot is not required to activate changes made to this
tunable. Any change made to the value of the tunable is effective immediately. However, the logical
block size is set per filesystem at mount time. The system administrator must unmount and re-mount
each filesystem after changing this tunable. Only NFSv3 mount points are affected by changing the
value of the nfs3_bsize tunable.
Modifying the Value
For NFS/TCP Filesystems:
To increase the transfer size of NFSv3 TCP requests, set the nfs3_bsize, nfs3_max_transfer_size, and
nfs3_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 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.
For NFS/UDP Filesystems:
To increase the size of NFSv3 UDP requests, set the nfs3_bsize, nfs3_max_transfer_size and
nfs3_max_transfer_size_clts tunables to the same value. Otherwise, the transfer size will default to the
smallest value of these three tunables.
To decrease the size of NFSv3 UDP requests, decrease the value of the nfs3_max_transfer_size_clts
tunable. For example, to decrease the size of I/O requests on all NFSv3 UDP filesystems to 8 KB, set
the value of nfs3_max_transfer_size_clts to 8192.
Caution: HP strongly discourages increasing
nfs3_max_transfer_size_clts above the default value of
32768 as this can cause NFS/UDP requests to fail. Also, 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 nfs3_bsize, nfs3_max_transfer_size,
nfs3_max_transfer_size_clts, or nfs3_max_transfer_size_cots
tunable value was changed while NFS filesystems were
mounted. The system administrator must unmount and re-
mount the NFS filesystem to use the new value.