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

2.1.12 nfs2_dynamic
Description
The nfs2_dynamic tunable controls the dynamic retransmission feature for NFSv2 mounted filesystems.
The dynamic retransmission feature is designed to reduce NFS retransmissions by monitoring server
response time and adjusting read and write transfer sizes on NFSv2 mounted filesystems using
connectionless transports such as UDP.
The nfs3_dynamic tunable controls the dynamic retransmission feature for NFSv3 mounted filesystems.
For more information, see nfs3_dynamic.
Tested Values
Default: 1 (Dynamic retransmission is enabled)
Min: 0 (Dynamic retransmission is disabled)
Max: 1
Restrictions on Changing
The nfs2_dynamic tunable is dynamic. System reboot is not required to activate changes made to this
tunable. However, the dynamic retransmission feature is set per filesystem at mount time. The system
administrator must unmount and re-mount each filesystem after changing this tunable. Only NFSv2
mount points are affected when you change the value of this tunable.
Modifying the Value
In congested networks, sending smaller sized NFS data packets can help if the network is dropping
larger data packets. Enabling this tunable enables you to adjust the read and write transfer sizes for
successful NFS I/O. If packets are not being dropped in the network, disabling this functionality
results in increased throughput. However, if the server response is delayed or the network is
overloaded, the number of timeouts can increase.
HP recommends leaving this tunable enabled because it helps the system minimize NFS packet loss
on congested networks.
2.1.13 nfs2_lookup_neg_cache
Description
The nfs2_lookup_neg_cache tunable controls whether a negative name cache is used for NFSv2
mounted filesystems. The negative name cache records file names that were looked up but not found.
This cache helps avoid over-the-wire lookups for files that are already known to be non-existent.
The nfs3_lookup_neg_cache tunable controls whether a negative name cache is used for NFSv3
mounted filesystems. The nfs4_lookup_neg_cache tunable controls whether a negative name cache is
used for NFSv4 mounted filesystems. For more information on these tunables, see:
• nfs3_lookup_neg_cache
• nfs4_lookup_neg_cache
Tested Values
Default: 1 (negative name cache will be used)
Min: 0 (negative name cache will not be used)
Max: 1
Restrictions on Changing
The nfs2_lookup_neg_cache tunable is dynamic. System reboot is not required to activate changes
made to this tunable. Only NFSv2 mount points are affected by changing the value of this tunable.