Bandwidth for Corosync only

[adriano_da_silva]

Would anyone know how much bandwidth Corosync uses?

I have some old 3COM switches of 10/100 Mb/s with 24 ports each. They are old, but they are in great condition. I am thinking of using them in a small Cluster of about 17 servers.

The idea would be to place two switches just to connect Corosync between the servers. I would use two network cards on each server just as link1 and link2 for Corosync. Other connections like Ceph and access to virtual machines and other services I would make on other network cards and other switches with more bandwidth, obviously.

Each link of Corosync I would connect to 1 10/100Mb/s switch. Link1 on Switch 1 and Link2 on Switch 2, this on each server. Then, all servers would have a network cable connected to switch 1 and another connected to switch 2, only for Corosync operation, with link redundancy.

Would it be a problem? Does Corosync traffic need more bandwidth?

It is quite common to use a 1 Gbps link for Corosync, but could using 100Mb/s full duplex have a synchronism problem?

Tanks;

 

[aaron]

I cannot chip in with experience but let me add the following:

Not sure if bandwidth will be a problem with a 17 node cluster as corosync really does not need a lot of it. The questions that come to mind and where I would definitely test this is latency as 100MBit is about 10x slower than 1GBit and then how good the backplane of those old switches is if there is traffic on almost all of the ports.