The nfsstat -s command

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The NFS server displays the number of NFS calls received, calls, and rejected, badcalls, due to authentication as well as the counts and percentages for the various kinds of calls made.

The following example shows the server part of the nfsstat command output specified by the -s option:

# nfsstat -s

Server rpc:
Connection oriented:
calls     badcalls  nullrecv badlen    xdrcall  dupchecks dupreqs
15835      0          0          0          0          772        0
Connectionless:
calls     badcalls  nullrecv badlen    xdrcall  dupchecks dupreqs
0          0          0          0          0          0          0

Server nfs:
calls      badcalls   public_v2  public_v3
15835      0          0          0
Version 2: (0 calls)
null       getattr    setattr    root       lookup     readlink   read
0 0%       0 0%       0 0%       0 0%       0 0%       0 0%       0 0%
wrcache    write      create     remove     rename     link       symlink
0 0%       0 0%       0 0%       0 0%       0 0%       0 0%       0 0%
mkdir      rmdir      readdir    statfs
0 0%       0 0%       0 0%       0 0%
Version 3: (15835 calls)
null       getattr    setattr    lookup     access     readlink   read
7 0%       3033 19%   55 0%      1008 6%    1542 9%    20 0%      9000 56%
write      create     mkdir      symlink    mknod      remove     rmdir
175 1%     185 1%     0 0%       0 0%       0 0%       120 0%     0 0%
rename     link       readdir    readdir+   fsstat     fsinfo     pathconf
87 0%      0 0%       1 0%       150 0%     348 2%     7 0%       0 0%
commit
97 0%

RPC output for the server, -s, is as follows:

calls: Total number of RPC calls received from clients
badcalls: Total number of calls rejected by the RPC layer
nullrecv: Number of times an RPC call was not available when it was thought to be received
badlen: Packets truncated or damaged (number of RPC calls with a length shorter than a minimum-sized RPC call)
xdrcall: Number of RPC calls whose header could not be External Data Representation (XDR) decoded
dupchecks: Number of RPC calls looked up in the duplicate request cache
dupreqs: Number of duplicate RPC calls found

The output also displays a count of the various kinds of calls and their respective percentages.

Duplicate checks are performed for operations that cannot be performed twice with the same result. The classic example is the rm command. The first rm command will succeed, but if the reply is lost, the client will retransmit it. We want duplicate requests like these to succeed, so the duplicate cache is consulted, and if it is a duplicate request, the same (successful) result is returned on the duplicate request as was generated on the initial request.

By looking at the percentage of calls for different types of operations, such as getattr(), read(), write(), or readdir(), you can decide what type of tuning to use. For example, if the percentage of getattr() calls is very high, then tuning attribute caches may be advantageous. If the percentage of write() calls is very high, then disk and LVM tuning is important. If the percentage of read() calls is very high, then using more RAM for caching files could improve performance.