1.1 NFS Characteristics

The NFS environment provides transparent file access to remote files over a network. File systems of remote devices appear to be local. Clients access remote file systems by using either the mount command or the automounter.

The NFS protocol enables multiple client retries and easy crash recovery. The client provides all the information for the server to perform the requested operation. The client retries the request until acknowledged by the server, or until it times out. The server acknowledges writes when the data has been flushed to nonvolatile storage.

The multithreaded kernel does not require the maintenance of multiple nfsd or asynchronous-block I/O daemon (biod) processes; they are both implemented as operating system kernel threads. There are no biods on the client and one nfsd process on the server.

NFS traffic is characterized by its randomness. NFS requests are generated in bursts, and they are usually of many types. The capacity of an NFS server must address the bursty nature of NFS file service demands. Demand varies widely, but is relatively predictable during normal days.

With regard to the types of requests from applications (which may be local or remote), most follow this pattern:

1. The user reads in the sections of the application binary, then executes the code pages leading to a user dialog, which specifies a data set on which to operate.

2. The application reads the data set from the (probably remote) disk.

3. The user can then interact with the application, manipulating the in-memory representation of the data (this phase continues for most of the runtime of the application).

4. The modified dataset is saved to disk.

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Note - More sections of the application binary may be paged in as the application continues to run in actions 2 through 4.

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1.2 Tuning Cycle

These tasks comprise the tuning cycles:

1. Measuring current performance and analyzing the data. See Chapter 3, "Analyzing NFS Performance."

2. Tuning for NFSops/second. See Chapter 4, "Configuration Recommendations for NFS Performance."

3. Repeating tasks 1 and 2 until no further improvements are required.

4. Reconfiguring new hardware on the server, if needed.

5. Repeating tasks 1 through 3 again.

1.3 Third Party Tools Used for NFS Performance Monitoring

Some of the third party tools you can use for NFS/networks include:

• ^(TM) · NetMetrix (Hewlett-Packard)
• ^(TM) · SharpShooter (AIM Technology)

1.4 Terminology

See the Glossary for definitions of words and phrases used in this book.