Throughout this book, we've used the output of nfsstat on both NFS clients and servers to locate performance bottlenecks or inefficient NFS architectures. The first two sections in this appendix summarize symptoms of problems identified from the output of nfsstat. The last list contains typical values for the error variable errno that may be returned by file operations on NFS-mounted filesystems.
Check the output of nfsstat -s for the following problems:
RPC requests are being rejected out of hand by the NFS server. This could indicate authentication problems caused by having a user in too many groups, attempts to access exported filesystems as root, or an improper Secure RPC configuration.
This indicates a malformed NFS request, detected by RPC or XDR protocol decoding on the server. This can be caused by bugs in the client or server, or by physical network problems.
The duplicate request cache keeps a record of previously executed NFS requests. The dupchecks counter tracks the number of times this cache was consulted, or checked. The dupreqs counter tracks the number of times a check of the cache had a "hit." In other words, dupreqs counts the number of times the NFS server received a previously executed request. For connection-oriented (TCP) requests, a high ratio of dupreqs to dupchecks is 0.01%. For connectionless (UDP) requests, a high ratio of dupreqs to dupchecks is ...