30.2 NSS Tuning Guidelines

Consider the following before you adjust the cache management parameters:

30.2.1 Before You Adjust Cache Parameters

Use Novell Remote Manager for NetWare to check memory usage statistics for NSS volumes.

IMPORTANT:Do not use the Monitor utility to check memory configuration and usage when running NSS volumes. The Cache Buffers statistics in Monitor apply only to NetWare Traditional file systems. Instead, use Novell Remote Manager for NetWare.

Before you adjust cache parameters, consider the following guidelines:

  • Make sure that you are running the latest version of NSS before adjusting parameters.

  • Do not split your resources between two file systems. Use NSS volumes only on your server, not a combination of NSS volumes and NetWare Traditional volumes.

    When the file system module (filesys.nlm) loads on NetWare, RAM that is not allocated elsewhere is given to the cache for the NetWare Traditional file system. When NSS loads, it also takes about 60% of the RAM that is not allocated elsewhere for NSS. Because the two file systems are disparate, this halves the performance of both caches. When applications load the amount of cache for both file systems, performance is reduced even further.

    If you must run multiple file systems, try to get to know the usage patterns of each system. This might enable you to balance RAM between them more effectively.

  • Purchase more memory, if needed to improve performance. If this is not an option, consider the tips in Section 30.2.2, Hints for Low Memory NetWare Systems.

30.2.2 Hints for Low Memory NetWare Systems

If your server has limited RAM resources, you can set some parameters to minimize the amount of RAM used for NSS.

NetWare ships with NSS configured for good performance on servers with at least 1 GB of memory. However, some servers might have less than 1 GB of memory, or memory might be dedicated to other services.

Consider the following when you need to reduce the memory footprint of NSS:

nss /ClosedFileCacheSize=value

The default value for ClosedFileCacheSize is 100000. Each entry uses about 1 KB of memory. On systems that only access a few files, this number can be reduced to 10000, which saves 90 MB of memory. This lower setting is not recommended for mail servers.

nss /MinBufferCacheSize=value

Some administrators turn off cache balancing but do not change the default value for MinBufferCacheSize. The default setting gives NSS too few cache buffers to use and results in poor performance. Set the MinBufferCacheSize to at least 10000 when your system uses only NSS volumes. Set it below 10000 only if you have NetWare Traditional file systems on your server. Because NSS freely gives cache buffers to the system, playing with cache balancing only helps systems running out of virtual address space.

30.2.3 The Tuning Process

Tuning NSS is a matter of modifying only one or two parameters at a time with a gradual, minor adjustment. Reset the cache performance statistics, then monitor the server for performance gains or degradation.

IMPORTANT:If you assign more memory to NSS than the server has available, NSS fails to load. To recover, see Section 30.2.4, Restoring Settings After a Failed Tuning Attempt

30.2.4 Restoring Settings After a Failed Tuning Attempt

If you give NSS more memory than the server has, NSS fails to load. Because your sys: volume is NSS-based, your server is inoperable until you load the server with an NSS override to correct the situation.

If you need to restore a setting after a failed tuning attempt, enter the following command at the server console:

server -z parameter

Replace parameter with the parameter you want to reset to its previous value, such as

server -z CacheBalance