Managing NFS and KRPC Kernel Configurations in HP-UX 11i v2 (Oct 2008)

respond to NFS requests using a different IP address than the client’s request originally used. For
example, on an HA/NFS server configured with an NFS package, the package will use a virtual IP
address. When a client sends an NFS request to the package (i.e. virtual) IP address, the server is not
required to send the reply back to the client using the same virtual IP address. The server may
substitute the real IP address configured on the physical LAN interface in place of the virtual IP
address.
In most cases this substituting of IP addresses by the server is ignored by the client and has no affect
on NFS behavior or performance. However, there have been reported cases where NFS client
systems reside behind a firewall and the firewall is configured to discard any packets that are replied
to using a different IP address than was originally requested. In these situations, NFS traffic is
interrupted and applications may appear to hang.
In these environments, the rpc_svc_ippktinfo_opt tunable should be enabled to force the NFS server to
respond to requests using the same IP address as was contained in the original request.
2.4.5 rpc_svc_maxthreads
Description
The rpc_svc_maxthreads tunable sets a limit on the maximum number of threads that an NFS server
can launch to service NFS requests for a single TCP connection.
When an NFS request arrives over a TCP connection, the server creates a thread to service the
request. When multiple NFS client requests arrive over a single TCP connection, threads are
dynamically created, and each thread picks up a request to service it. Once the thread finishes
servicing, and is idle for some time, the thread is destroyed. The maximum number of threads the
server can launch to service multiple NFS requests over a single TCP connection is limited by the value
of this tunable.
Tested Values
Default: 10
Min: 1
Max: 10
Note: If the tunable is set to a value greater than 10, an
informational warning is issued at runtime. This value is
outside the tested limits.
Restrictions on Changing
The rpc_svc_maxthreads tunable is dynamic. Changes made to this tunable are applicable for TCP
connections that are created after the value of this tunable is modified. System reboot is not required
to activate a change made to this tunable.
Modifying the Value
Care must be taken while modifying the value of this tunable. Modifying the tunable affects the
number of kernel threads allowed for every NFS/TCP connection and affects the total number of
threads running on the server system. To handle the extra threads the server’s kernel is tuned by
modifying nkthread, max_thread_proc and ncallout tunables.
This tunable is not available in the next release of HP-UX. Starting with the HP-UX 11i v3 release, NFS
thread management uses a different mechanism to handle the service threads.
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