[ILUG] Heartbeat and intelligent switches

[Paul Jakma]

On Mon, 6 Jun 2005, Colm MacCarthaigh wrote:

> Yes, but it gets you very reliable L3 failover :) The end-result is 
> the same.

Not quite.

Stuff like heartbeat fails across to /other/ machines. They're 
complementary, i could imagine one using both heartbeat (to fail-over 
between 2 machines) and bonding (to balance/failover between NICs on 
one box).

> Although we use the bonding driver, we are not doing 
> channel-bonding.  Our aim is not to balance, but we do use it to 
> team interfaces in order to have a resilient MAC, which can operate 
> on either interface (but only one at a time). This is effectively 
> exactly the same as the L3 failover, only a layer lower.

Aye.

That'd work too. For one box.

> Our backup ports are on a different switch. You don't think we'd 
> make our servers resilient and then plug them into one switch do 
> you? ;) Our services network has multiple switches, as long as 
> their in the same spanning-tree mesh, it works out fine :)

Right :)

I'd be worried about odd artifacts though and/or hitting strange bugs 
in switch firmware.

> There are other L3 failover options. Lately we're using OSPF as a 
> L3 resilience mechanism to servers (Colin knows more about this), 
> and it's working out quite well

Longer convergence time though with OSPF. Lowest you can set 
dead-time is likely about 5s.

> (many thanks to your Quagga efforts).

:)

And the other maintainers too.

> And for the next iteration of ftp.heanet.ie we're planning to 
> distribute 4Gb/sec of connectivity via equal-cost static routes.

Wowser.

> So, if the network really is expensive and shiny, there's always 
> those kinds of options also.

Aye.

Many of these things are complementary, as I said above. You could 
conceivably use all of bonding, IP failover and OSPF together. Each 
one providing a slightly different part of the HA puzzle (OTOH, it 
could be really fun to debug problems in such a case..).

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
Fortune:
He who is good for making excuses is seldom good for anything else.