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your attention on the following set of values reporting the current disk and network activity. Note that the previous example does not show the cumulative statistics. The output shown represents the second set of values, which report the I/O statistics within the last 20 seconds. The first two lines represent the header, then every disk and NFS filesystem on the system is presented in separate lines. The first line reports statistics for the local hard disk c0t0d0. The second line reports statistics for the local floppy disk fd0. The third line reports statistics for the volume manager vold. In Solaris, the volume manager is implemented as an NFS user-level server. The fourth and fifth lines report statistics for the NFS filesystems mounted on this host. Included in the statistics are various values that will help you analyze the performance of the NFS activity:

r/s

Represents the number of read operations per second during the time interval specified. For NFS filesystems, this value represents the number of times the remote server was called to read data from a file, or read the contents of a directory. This quantity accounts for the number of read, readdir, and readdir+ RPCs performed during this interval. In the previous example, the client contacted the server assisi an average of 34.1 times per second to either read the contents of a file, or list the contents of directories.

w/s

Represents the number of write operations per second during the time interval specified. For NFS filesystems, this value represents the number of times the remote server was called to write data to a file. It does not include directory operations such as mkdir, rmdir, etc. This quantity accounts for the number of write RPCs performed during this interval.

kr/s

Represents the number of kilobytes per second read during this interval. In the preceding example, the client is reading data at an average of 1,092.4 KB/s from the NFS server assisi. The optional -M directive would instruct iostat to display data throughput in MB/sec instead of KB/sec.

kw/s

Represents the number of kilobytes written per second during this interval. The optional -M directive would instruct iostat to display data throughput in MB/sec.

wait

Reports the average number of requests waiting to be processed. For NFS filesystems, this value gets incremented when a request is placed on the asynchronous request queue, and gets decreased when the request is taken off the queue and handed off to an NFS async thread to perform the RPC call. The length of the wait queue indicates the number of requests waiting to be sent to the NFS server.

actv

Reports the number of requests actively being processed (i.e., the length of the run queue). For NFS filesystems, this number represents the number of active NFS async threads waiting for the NFS server to respond (i.e., the number of outstanding requests being serviced by the NFS server). In the preceding example, the client has on average 3.2 outstanding RPCs pending for a reply by the server assisi at all times during the interval specified. This number is controlled by the maximum number of NFS async threads configured on the system. Chapter 18 will explain this in more detail.

wsvc_t

Reports the time spent in the wait queue in milliseconds. For NFS filesystems, this is the time the request waited before it could be sent out to the server.

asvc_t

Reports the time spent in the run queue in milliseconds. For NFS filesystems, this represents the average amount of time the client waits for the reply to its RPC requests, after they have been sent to the NFS server. In the preceding example, the server assisi takes on average 93.2 milliseconds to reply to the client's requests, where the server paris takes 336.7 milliseconds. Recall that the server assisi and the client are physically connected to the same hub, whereas packets to and from the server paris have to traverse multiple switches to communicate with the client. Analysis of nfsstat -s on paris indicated a large amount of NFS traffic directed at this server