The answer is best determined by the network administrator, but only after careful analysis. Often, the answer is a combination of both perspectives...

Although a properly tuned Server rarely needs to be downed and restarted, almost all Servers should be downed and restarted periodically to reclaim fragmented memory. While Novell has dramatically improved memory management in NetWare v4, there are still cases where memory gets fragmented in the Server. Some of the problem lies in Novell's reallocation of memory for internal tables (such as conection tables, FAT tracking, NDS tables, directory buffers, packet receive buffers, routing information, etc.).

Another problem is that some NLMs are not designed to properly manage their memory requirements. Many such NLMs will dynamically allocate and free a block of memory repeatedly, often in very small sizes, for temporary storage rather than allocating and designating a fixed memory block for use, as required. The repeated allocation and release of such small blocks of memory can create significant fragmentation when combined with other memory allocation and reallocation requirements.

Memory fragmentation aside, proper tuning of a Server is another challenge network administrators must face. Since NetWare will dynamically tune itself to the ever changing loads it encounters, it will most often become tuned to worst case scenarios or exception events. Such tuning does not necessarily guarantee best overall performance.

Is the load placed on the Server by doing a full Backup or an Anti-Virus scan representative of normal operations? Chances are that it is not. Yet, both applications are widely used in real world environments and impact the Server in such a way as to cause it to tune itself to the load.

So how can a network administrator maximize the Server's dynamic tuning capabilities and protect against such adverse tuning? The key is in the SET Parameters provided in NetWare. The SET Parameters are most often used when a network administrator encounters a bottleneck or notices that a previously defined maximum value has been reached. In such cases, the network administrator, on their own or at the advice of others who may not be fully versed on the specifics of the environment, will bump the values without understanding the full impact of the adjustment. These types of arbitrary changes can also prove to generate a negative impact on the Server.

Most of the SET Parameters which are specific to the tuning of the Server have minimum and maximum values. When properly defined, the minimums insure that the Server restarts in a pre-tuned state while the maximums define the limits to Server self-adjustment to protect against adverse tuning. The challenge is to validate the optimal minimum and maximum levels then specify them in the STARTUP.NCF or AUTOEXEC.NCF file.

The following describes one method which can be used for optimal Server tuning:

1. Down the Server and restart it at the beginning of a normal business day. Allow the Server to run all day under normal load and operations.


2. Prior to initiating any Backup, Anti-Virus scans, or other such periodic events which create non-typical Server load, record how the Server has tuned itself. Record the current, tuned values for the Directory Cache Buffers, Packet Receive Buffers, and Service Processes.


- If any have reached their maximum allowed values, increase the appropriate SET Parameter by a factor of 25% (rounded up).


- The current, tuned values for the Buffer statistics should become the new minimum values for their appropriate SET Parameter.


Note: Use the MONITOR NLM or some other utility, such as avanti's NConsole Server Trends Analysis utility, to view the current levels. NConsole can generate SET Parameter reports and perform SET Parameter deviation or variance reports between Servers to make this task easier.




3. Add the appropriate SET Parameters with the new minimum and, if appropriate, maximum values to the STARTUP.NCF or AUTOEXEC.NCF file, as appropriate.


Note: You will need to read the description of the SET Parameter to determine which .NCF file is appropriate. If using avanti's NConsole Server Trend Analysis utility, any change to a SET Parameter will result in a prompt for addition to the appropriate file.



4. Repeat steps 1 through 3 for a few days until the values appear to have stabilized.


5. Calculate the maximum values to represent 125% of the minimum values (rounded up), then add the associated SET Parameters to the STARTUP.NCF or AUTOEXEC.NCF file, as appropriate.


6. Perform these tuning procedures at least once per quarter or whenever any significant load or configuration changes occur. Be sure to start with the already determined minimums and increase the maximums to allow for increased load tuning.

Serious tuning requires long-term trends analysis and capacity planning that can help identify bottlenecks before they occur, while insuring optimal performance and configuration. Since Novell does not provide such tools within NetWare, add-on utilities must be considered for those wishing to proactively monitor and plan for their network.