Increasing NSS Read Performance under OES2 Linux

With the shipping version of OES2 Linux, the read performance of NSS volumes is significantly slower than that of native Linux filesystems.

This issue is resolved in the oes2-novell-nss-5503-0 patch, which was released on August 21, 2008. This patch should be downloaded and installed through rug.

In this new version of NSS, the problem has been resolved through a configurable NSS global called "UnplugAlways". At this time, this global is disabled by default.

The following steps can be used to enable UnplugAlways:

• Launch
  
  nsscon
• To enable UnplugAlways, enter the following:
  
  nss /UnplugAlways
• To disable UnplugAlways, enter the following:
  
  nss /noUnplugAlways

Neither of the above commands sets the global value persistently.  Therefore, this setting will be lost upon server restart. To avoid this, the text "/UnplugAlways" should be added to the /etc/opt/novell/nss/nssstart.cfg file.

The following command can be used to display the current value of the UnplugAlways global:

   echo -e "nss /help\nc\nexit\n" | nsscon | sed 's/\x1b\[[^m]*m//g' | grep -A1 UnplugAlways

The 'sed' command is used to remove all of the color information that 'nsscon' outputs.  Without this command the shell's background color will be changed and not restored to its original color. The output of this command should generate the following when UnplugAlways is enabled.

/(No)UnplugAlways    If ON, unplugs the device queue
                     after queuing each read bio.
                     [Value=ON]
 

Please note that modification of this parameter is only beneficial for the OES2 FCS (or shipping) code for NSS.

When using NSS file systems on OES2 with patch levels beyond FCS, please verify the UnplugAlways parameter is disabled again (value is set to OFF), or disable this as suggested in the resolution field above.