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

Tested Values
The nfs4_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 the
filesystem after changing this tunable. Only NFSv4 mount points are affected by changing the value
of the nfs4_bsize 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
administrator must unmount and re-mount the NFS filesystem
to use the new value.
Note: The nfs4_bsize tunable affects every NFSv4 filesystem.
To control the transfer sizes of specific NFS filesystems, use
the rsize and wsize mount options. Refer to the
mount_nfs(1M) man page for more information.
2.1.35 nfs4_cots_timeo
Description
The nfs4_cots_timeo tunable controls the default RPC timeout for NFSv4 mounted filesystems using a
connection-oriented transport such as TCP.
The nfs2_cots_timeo tunable controls the default RPC timeout for NFSv2 mounted filesystems. The
nfs3_cots_timeo tunable controls the default RPC timeout for NFSv3 mounted filesystems. For more
information on these tunables, see:
• nfs2_cots_timeo
• nfs3_cots_timeo