Technical data

NFS Server
20.15 Improving NFS Server Performance
20.15.3 Increasing the Number of Active Threads
The NFS server is an asynchronous, multithreaded process. This means that
multiple NFS requests can be processed concurrently. Each NFS request
is referred to as a thread. With increased server activity, client users may
experience timeout conditions. Assuming the server host has the available
resources (CPU, memory, and disk speed), you can improve server response by
increasing the number of active threads. You do this by changing the value for
the appropriate NFS server attributes, as described in Section 20.12.
The NFS server supports both TCP and UDP connections. You can control the
maximum number of concurrent threads for each type of connection.
• To set the maximum number of TCP threads, set the tcp_threads attribute.
• To set the maximum number of UPD threads, set the udp_threads attribute.
Do not set the UDP maximum threads to zero. If you set the variable to zero, the
protocol will be disabled.
If you increase the number of active threads, you should also consider increasing
the timeout period on UNIX clients. You do this with the /TIMEOUT option to
the TCP/IP Services MOUNT command.
If your clients still experience timeout conditions after increasing the number of
active threads and the timout period on the client, you may need to upgrade your
hardware.
20.15.4 OpenVMS SYSGEN Parameters That Impact Performance
The following OpenVMS SYSGEN parameters impact NFS server performance:
• CHANNELCNT
The CHANNELCNT parameter sets the maximum number of channels that
a process can use. Ensure that CHANNELCNT is set large enough to handle
the total number of files accessed by all clients.
Note
The NFS server process is also limited by the FILLM of the TCPIP$NFS
account’s SYSUAF record. The effective value is the lower of the FILLM
and CHANNELCNT values.
• ACP parameters
The NFS server issues a large number of ACP QIO calls through CFS.
Altering certain ACP parameters could yield better performance. If you have
reliable disks, you may want to set the parameter ACP_DATACHECK to zero
to avoid extra disk I/Os. Directory searching and file attribute management
constitutes a majority of the ACP operations. Therefore, Compaq recommends
that you increase parameters such as ACP_HDRCACHE, ACP_MAPCACHE,
ACP_DIRCACHE, ACP_FIDCACHE, and ACP_DATACACHE.
• LOCK parameters
The various lock manager parameters may need some alteration because CFS
uses the lock manager extensively. A lock is created for each file system, each
referenced file, and each data buffer that is loaded into the CFS cache.
NFS Server 20–21