HP Tru64 UNIX and TruCluster Server Version 5.1B-5 Patch Summary and Release Notes (March 2009)

• Avoid congestion on your LAN and cluster interconnect.
• Ensure your servers have enough excess capacity to respond quickly to NFS
requests that modify the file system (writes, file and directory creation, and so
forth.)
• Increase the size of the server's duplicate request cache when the nfsstat
command shows a large number of retransmits to clients. For instructions on
increasing the size of the cache, see “Tuning the NFS Server Duplicate Request
Cache”.
You can monitor the number of NFS retransmissions using the nfsstat -c command.
The retrans field indicates the number of retransmissions. A retransmission rate
higher than 2% indicates a potential problem.
The following example shows the output from the nfstat -c command. The
retransmission fields are marked with asterisks (*). This example is of a client
workstation in a typical environment.
% nfsstat -c
Client rpc:
tcp: calls badxids badverfs timeouts newcreds
0 0 0 0 0
creates connects badconns inputs avails interrupts
0 0 0 0 0 0
udp: calls badxids badverfs timeouts newcreds *retrans*
224518870 959 0 101985 0 0
badcalls timers waits
102013 110894 0
Client nfs:
calls * retrans* badcalls nclget nclsleep ndestroys ncleans
224414222 4248 28 224414282 0 6219 224408063 \
If an overwhelmed duplicate request cache condition occurs, we recommend you
perform one or more of the following tasks:
• Ensure that there are short periods of idle time on the I/O subsystem and network
links.
• After a file is written, do not rewrite it for a few minutes.
• Delete and recreate files instead of overwriting the same file repeatedly.
• Use Memory Channel cluster interconnect.
To avoid overwhelming the duplicate request cache:
• Do not run hundreds of simultaneous processes that write files
• Do not operate the system under so heavy a load that NFS operations frequently
take several seconds to complete.
3.2 Prior Release Notes 71