Re: 2 box LVS with HA

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: 2 box LVS with HA
Cc: keepalived-devel@xxxxxxxxxxxxxxxxxxxxx
From: Alexandre Cassen <Alexandre.Cassen@xxxxxxxxxx>
Date: Sat, 27 Jul 2002 14:52:08 +0200
Hi Nenad,

i got keepalived to failover a ip-adress from A to B,
and back again when A starts up.

So far so good -
but it does not loadbalance the requests.
when the IP is on A then i only get responses from A,
B shows some entries with ipvsadm - but it looks like it thinks it is the director
and vice versa.

No :) This another point I need to document :

Imagine the follwoing scenario :

o You have built an active/passive configuration for your LVS cluster
o Host A is MASTER and host B BACKUP

when you run Keepalived on both and run 'ipvsadm -ln' then you will see that LVS topology appear on both director. :) Ones can say : "Hey it is not working since I see both configuration on both director even on the BACKUP...".

Then software design implemented here is to speed up IP takeover for A to B. Since VIP is only owned by MASTER director (A in normal state) then all LVS topology will be only accessible from A director. So if this topology is set on B it is not a problem since all traffic will be directed on host A. But, to minimize IP LVS availibility during VRRP IP takeover, then it is better if lVS rulez are already set :) then the keepalived framework will only activate healthcheckers for this VIP.

So if VIP is on A in normal state then LVS topology will appear on A & B (normal, implementation choice). Since VIP is not on B then healtcheckers on B will not be activated to not overload the realserver since it is not needed. If A fire then B become MASTER and VIP is now owned on LVS B then healtcheckers are activated. VIP presence drive healtcheckers activity.

Is it enough to configure keepalived, or do i have to do something additional ?

No need to configure any other tools.

Btw. Keepalived does not work with my RTL-8139 based Cards,
it only reports "ethx down".
I switched to some 3Com cards which seem to work fine.

Yes, since I don t have realteck NIC I can not debug this issue.

Best regards,

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