Performance Management Guide

Tuning AIX Fast Connect

All of the following tuning options were investigated using a freely available file server benchmark called Netbench from ZD, Inc. Printing performance is not discussed in this appendix, nor is any specific capacity-planning information.

• AIX Fast Connect Tuning Options

  The suggested method of configuring AIX Fast Connect for Windows is to use installed Web-based System Manager or terminal-based (smitty smb) configuration tools. The following options may be used in the /etc/cifs/cifsConfig file and have an effect on file server performance. See the AIX 5L Version 5.1 System Management Guide: Communications and Networks for more information concerning the options listed below:

  accesscheckinglevel (0, 1)

  Enables support for a fast-path access-checking subroutine. It assumes that the process has permissions to access all file paths in the system. It avoids a longer RPC based authentication mechanism.

  cache_searches (0, 1)

  Note:

  This option is only available in AIX Version 3

  This option enables caching of the shared filesystems directories information within the CIFS server. If search caching is needed, this parameter should be enabled as well as the per share directory caching option.

  casepreserve (0, 1) and casesensitive (0, 1)

  Request the server to preserve case and to recognize uppercase and lowercase during file-name matching operations. You may not be able to simplify the complex searches because of client requirements.

  del_inactive_searches (0,1)

  When enabled, this option deletes inactive search handles left open by the clients.

  dosfilenamemapping (0, 1)

  Controls how long file names are mapped to 8.3 format. If enabled, long file names are mapped into the DOS 8.3 format. Disabling DOS file-name mapping is more efficient.

  filenamematchinglevel (0, 1)

  Enables case-insensitive matching. You may be able to disable this option depending on the client you are using. Disabling case sensitivity matching improves performance. This option is superseded by casepreserve and casesensitive options.

  oplockfiles (no, yes)

  Enables opportunistic locking support in the AIX Fast Connect for Windows server. The default is yes and should be enabled for best possible performance. This configuration option can have a very large impact on file-server performance.

  send_file_api (0, 1)

  Enables support for the sendfile API from the AIX Fast Connect Server for Windows. This option will use the built-in Network Buffer Cache system support. If you turn this option on, test with the Network Buffer Cache enabled to see if your file server traffic benefits from this operating system feature. You might find better performance using the sendfile API without the Network Buffer Cache network option enabled (nbc_limit = 0). See the no command option for more information on configuring the Network Buffer Cache subsystem.

  send_file_cache_size (default 1048576)

  Determines the largest read value where the sendfile API will cache the file. Tune this value depending on your own specific environment.

  send_file_size (default 4096)

  Determines the smallest read size that will use the sendfile API. This is the low-water mark for caching read requests. Tune this value depending on your own specific environment.

  statistics (0, 1)

  Enables and disables the collection of server statistics that can be viewed using the net statistics command. If you set this option to zero, the output from the net statistics command will show zero totals. It does not constitute a large amount of overhead.

• Operating System Tuning

  The AIX Fast Connect for Windows server runs in the application space and is a threaded application. The AIX Fast Connect for Windows server uses the pthread library. Export the following environment variables from the shell before starting the AIX Fast Connect for Windows server. The best performance is achieved on MP servers by running with the malloc multiheap support and one kernel thread to one runnable pthread.

  • AIXTHREAD_SCOPE=S
  • AIXTHREAD_MNRATIO=1:1
  • MALLOCMULTIHEAP=1

  You can also disable debugging in libpthreads.a before you start the cifsServer program.

  • AIXTHREAD_RWLOCK_DEBUG=OFF
  • AIXTHREAD_COND_DEBUG=OFF
  • AIXTHREAD_MUTEX_DEBUG=OFF

  If you encounter problems debugging applications that use libpthreads.a, you can turn the debugging options back on until you have a stable application.

• NetBench Configuration Options

  Shown below are suggested configurations changes for the AIX Fast Connect for Windows Server if you want to run with the NetBench benchmarking software. This configuration assumes that you will be running with Microsoft NT v4.0 clients at SP5 or higher. These settings also assume that you have set the AIX Network Buffer Cache (nbc_limit) to zero.

  Following are suggested changes to the initial default configuration parameters in the /etc/cifs/cifsConfig file:

  • For Netbench version 6.0:
    • encrypt_passwords=1
    • statistics = 0
    • send_file_api = 1
    • dosfilenamemapping = 0
    • filenamematchinglevel = 1
    • casepreserve = 1
    • casesensitive = 0
    • accesscheckinglevel = 0
    • del_inactive_searches=1
    • cache_searches=1