HA logic question

[pipboy]

Sorry if this has been answered before. Could not find the exact answer I was looking for. I understand the three server HA setup with use of a SAN and it seems simple enough.. My problem is planning for the future.

What happens when you have , lets say... 10 servers. You place the load on half of the servers, and leave the other half available for fail over. During fail over, how do we stop the 5 servers' load from stacking up on the first available server? Do we have to create a separate fail over domain for each pair of servers? ie, Server A and Z are one fail over domain and server B and Y are in another? I could imagine this being pretty costly on equipment.

Thanks for your time

 

[pipboy]

just a daily bump (im still here)

 

[tom]

Your question is unclear. If you configure HA and one physical host fails the HA manager starts the VM´s on one of the remaining hosts. its very unlikely that 5 physical hosts fail in the same moment.

Optinally, you can define failover domains - by doing this, you define the possible hosts for your HA VMs.

 

[pipboy]

thank you for your response

"HA manager starts the VM´s on one of the remaining hosts"
ok, lets say a server at 90% load fails, and then it picks one of the available hosts. Now, lets say another server (running at a high load) fails, how does the VM know to not pick the same server to fail over too? If both VM's failed over to the same host, then there would not be enough resources on that Host... In short, during a fail over, does ProxMox take Host server load into account when deciding where to put a VM?

 

[e100]

I am not really sure how it selects what node to start the failed service on.

Failover Domains would allow you to control where things would run by placing priorities on the nodes within the failover domain.