Communications I/O

Values suggested here reflect evaluations made at the time this documentation was written. For the latest system configuration and tuning settings, see Configuring and tuning your system for GPFS.

To optimize the performance of GPFS and your network, it is suggested you do the following:
  • Enable Jumbo Frames if your switch supports it.

    If GPFS is configured to operate over Gigabit Ethernet, set the MTU size for the communication adapter to 9000.

  • Verify /proc/sys/net/ipv4/tcp_window_scaling is enabled. It should be by default.
  • Tune the TCP window settings by adding these lines to the /etc/sysctl.conf file: 
    # increase Linux TCP buffer limits
net.core.rmem_max = 8388608
net.core.wmem_max = 8388608
# increase default and maximum Linux TCP buffer sizes
net.ipv4.tcp_rmem = 4096 262144 8388608
net.ipv4.tcp_wmem = 4096 262144 8388608
    After these changes are made to the /etc/sysctl.conf file, apply the changes to your system:
    1. Issue the sysctl -p /etc/sysctl.conf command to set the kernel settings.
    2. Issue the mmshutdown -a command and then issue mmstartup -a command to restart GPFS