min_free_kbytes Setting

This topic details how to update the min_free_kbytes setting so that it is within the range supported by Vertica. The installer reports this issue with the identifier: S0050 if the setting is too low, or S0051 if the setting is too high.

The vm.min_free_kbytes setting configures the page reclaim thresholds. When this number is increased the system starts reclaiming memory earlier, when its lowered it starts reclaiming memory later. The default min_free_kbytes is calculated at boot time based on the number of pages of physical RAM available on the system.

The setting must be the greater of:

The installer automatically configures the correct setting if the default value does not meet system requirements. If there is an issue setting this value, or you have used the --no-system-configuration argument to the installer and the current setting is incorrect, then the installer reports this as an issue.

All Systems

To manually set min_free_kbytes:

  1. Determine the current/default setting with the following command:
  2. /sbin/sysctl vm.min_free_kbytes
  3. If the result of the previous command is No such file or directory or the default value is less than 4096, then run the command below:
  4. memtot=`grep MemTotal /proc/meminfo | awk '{printf "%.0f",$2}'`
    echo "scale=0;sqrt ($memtot*16)" | bc
  5. Edit or add the current value of vm.min_free_kbytes in /sbin/sysctl.conf with the value from the output of the previous command.
  6. # The min_free_kbytes setting


  7. Run sysctl -p to apply the changes in sysctl.conf immediately.
  8. Note: These steps will need to be replicated for each node in the cluster.