Thursday, May 1, 2008

Configure Jumbo Frames to Boost Network Performance / Throughput

Jumbo frames are Ethernet frames with more than 1500 bytes of payload MTU. Most modern Linux distros (Kernel 2.6.17+) support frames larger than 1500 bytes.

First, make sure your network driver supports custom MTU. Second you need to have a compatible gigabit NIC and switch (such as Cisco Catalyst 4000/4500 Switches with Supervisor III or Supervisor IV ) that is jumbo frame clean.

Jumbo frames can reduce server overhead such as a big decrease in CPU usage when transferring larger file. Also you should see some increase in network throughput.

Configure eth0 interface for Jumbo Frames. Warning! These examples depend upon a compatible network gear such gigabit Ethernet switches and gigabit Ethernet network interface cards.
# ifconfig eth0 mtu 9000

To make changes permanent, append the
directive into the network configuration file for eth0.
# vi /etc/sysconfig/network-script/ifcfg-eth0 # Redhat/CentOS/Fedora

# vi /etc/network/interfaces # Debian/Ubuntu

# /etc/init.d/networking restart

To confirm the MTU used between two specific devices:
# ip route get {IP-address}
# ip route get dev eth0 src
cache mtu 9000 advmss 1460 hoplimit 64

Application Protocol Tunning. You may need to tune the application/network protocol such as NFS and SMB to take advantage of Jumbo Frames.

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