Full Mesh Network for Ceph Server

Introduction

This wiki page describes how to configure a three node "Meshed Network" Proxmox VE (or any other Debian based Linux distribution), which can be, for example, used for connecting Ceph Servers or nodes in a Proxmox VE Cluster with the maximum possible bandwidth and without using a switch. This can also work with bigger clusters, in general you need (number_of_nodes - 1) NIC ports on each node, e.g.: you'd need 4 NIC ports for a 5-node full mesh. A big advantage of this setup is the fact, that you can achieve a fast network connection with 10, 40, or more GBit/s bandwidth WITHOUT buying an expensive fast-enough network switch.

There a two possible method to achieve a full mesh:

1. Routed: Each packet is sent to the addressed node only
2. Broadcast: Each packet is sent to both other nodes

The routed setup is generally recommended. It uses less bandwidth and detects error states more reliably. The advantage of the broadcast method is an easier setup process.

Example

3 servers:

• Node1 with IP addresses x.x.x.50
• Node2 with IP addresses x.x.x.51
• Node3 with IP addresses x.x.x.52

3 to 4 Network ports in each server:

• ens18, ens19 will be used for the actual full mesh. Physical direct connections to the other two servers, 10.15.15.y/24
• ens20 connection to WAN (internet/router), using at vmbr0 192.168.2.y
• ens21 (optional) LAN (for cluster traffic, etc.) 10.14.14.y

Direct connections between servers:

• Node1/ens18 - Node2/ens19
• Node2/ens18 - Node3/ens19
• Node3/ens18 - Node1/ens19

                    +-----------+
                    |   Node1   |
                    +-----------+
                    |ens18|ens19|
                    +--+------+-+
                       |      |
        +-----+        |      |       +-----+
+-------+ens18+-----------+   +-------+ens18+-------+
| Node2 +-----+        |  |           +-----+ Node3 |
+-------+ens19+--------+  +-----------+ens19+-------+
        +-----+                       +-----+

Recommended: Routed Setup

Corresponding to the above described setup example the 3 nodes have to be configured as described in the following sections. Note that multicast is not possible with this method.

Node1

/etc/network/interface

auto lo
iface lo inet loopback

iface ens20 inet manual

auto ens21
iface ens21 inet static
        address  10.14.14.50
        netmask  255.255.255.0

# Connected to Node2 (.51)
auto ens18
iface ens18 inet static
        address  10.15.15.50
        netmask  255.255.255.0
        up ip route add 10.15.15.51/32 dev ens18
        down ip route del 10.15.15.51/32

# Connected to Node3 (.52)
auto ens19
iface ens19 inet static
        address  10.15.15.50
        netmask  255.255.255.0
        up ip route add 10.15.15.52/32 dev ens19
        down ip route del 10.15.15.52/32

auto vmbr0
iface vmbr0 inet static
        address  192.168.2.50
        netmask  255.255.240.0
        gateway  192.168.2.1
        bridge_ports ens20
        bridge_stp off
        bridge_fd 0

route

root@pve-2-50:~# ip route
default via 192.168.2.1 dev vmbr0 onlink 
10.14.14.0/24 dev ens21 proto kernel scope link src 10.14.14.50 
10.15.15.0/24 dev ens18 proto kernel scope link src 10.15.15.50 
10.15.15.0/24 dev ens19 proto kernel scope link src 10.15.15.50 
10.15.15.52 dev ens19 scope link 
10.15.15.51 dev ens18 scope link 
192.168.0.0/20 dev vmbr0 proto kernel scope link src 192.168.2.50 

Node2

/etc/network/interface

auto lo
iface lo inet loopback

iface ens20 inet manual

auto ens21
iface ens21 inet static
        address  10.14.14.51
        netmask  255.255.255.0

# Connected to Node3 (.52)
auto ens18
iface ens18 inet static
        address  10.15.15.51
        netmask  255.255.255.0
        up ip route add 10.15.15.52/32 dev ens18
        down ip route del 10.15.15.52/32

# Connected to Node1 (.50)
auto ens19
iface ens19 inet static
        address  10.15.15.51
        netmask  255.255.255.0
        up ip route add 10.15.15.50/32 dev ens19
        down ip route del 10.15.15.50/32

auto vmbr0
iface vmbr0 inet static
        address  192.168.2.51
        netmask  255.255.240.0
        gateway  192.168.2.1
        bridge_ports ens20
        bridge_stp off
        bridge_fd 0

route

root@pve-2-51:/# ip route
default via 192.168.2.1 dev vmbr0 onlink 
10.14.14.0/24 dev ens21 proto kernel scope link src 10.14.14.51 
10.15.15.0/24 dev ens18 proto kernel scope link src 10.15.15.51 
10.15.15.0/24 dev ens19 proto kernel scope link src 10.15.15.51 
10.15.15.52 dev ens18 scope link 
10.15.15.50 dev ens19 scope link 
192.168.0.0/20 dev vmbr0 proto kernel scope link src 192.168.2.51 

Node3

/etc/network/interface

auto lo
iface lo inet loopback

iface ens20 inet manual

auto ens21
iface ens21 inet static
        address  10.14.14.52
        netmask  255.255.255.0

# Connected to Node1 (.50)
auto ens18
iface ens18 inet static
        address  10.15.15.52
        netmask  255.255.255.0
        up ip route add 10.15.15.50/32 dev ens18
        down ip route del 10.15.15.50/32

# Connected to Node2 (.51)
auto ens19
iface ens19 inet static
        address  10.15.15.52
        netmask  255.255.255.0
        up ip route add 10.15.15.51/32 dev ens19
        down ip route del 10.15.15.51/32

auto vmbr0
iface vmbr0 inet static
        address  192.168.2.52
        netmask  255.255.240.0
        gateway  192.168.2.1
        bridge_ports ens20
        bridge_stp off
        bridge_fd 0

route

root@pve-2-52:~# ip route
default via 192.168.2.1 dev vmbr0 onlink 
10.14.14.0/24 dev ens21 proto kernel scope link src 10.14.14.52 
10.15.15.0/24 dev ens18 proto kernel scope link src 10.15.15.52 
10.15.15.0/24 dev ens19 proto kernel scope link src 10.15.15.52 
10.15.15.51 dev ens19 scope link 
10.15.15.50 dev ens18 scope link 
192.168.0.0/20 dev vmbr0 proto kernel scope link src 192.168.2.52 

Broadcast setup

Create a "broadcast" bond with the given interfaces on every node. This can be done over the GUI or on the command-line.

GUI

On the GUI go to the node level -> System -> Network. Then click on "Create" and select "Linux Bond". In the Wizard make your configuration without a gateway and set mode to "broadcast".

Reboot the node to activate the new network settings.

Command-Line

Add the following lines to '/etc/network/interfaces'.

auto bond<No>
iface bond<No> inet static
	address  <IP>
	netmask  <Netmask>
	slaves <Nic1> <Nic2>
	bond_miimon 100
	bond_mode broadcast
#Full Mesh

Then start the bond

ifup bond<No>

In Node1 of the above described setup example /etc/network/interface will look like as follows:

iface lo inet loopback

iface ens20 inet manual

auto ens21
iface ens21 inet static
        address  10.14.14.50
        netmask  255.255.255.0


iface ens18 inet manual

iface ens19 inet manual

auto bond0
iface bond0 inet static
       address 10.15.15.50
       netmask 255.255.255.0
       slaves ens18 ens19
       bond_miimon 100
       bond_mode broadcast


auto vmbr0
iface vmbr0 inet static
        address  192.168.2.50
        netmask  255.255.240.0
        gateway  192.168.2.1
        bridge_ports ens20
        bridge_stp off
        bridge_fd 0