Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
----- Original Message -----
From: "Lars Ellenberg" <Lars.Ellenberg at linbit.com>
To: <drbd-user at nudlaug.linbit.com>
Sent: Saturday, January 24, 2004 10:01 AM
Subject: Re: [DRBD-user] drbd heartbeat help
> / 2004-01-24 08:06:32 +0100
> \ Dominique Chabord:
> > > I think having 192.168.1.2 as your "floating" ip while having
> > > 192.168.1.{3,4} as your drbd ips is asking for trouble.
> > > most likely drbd has problems to bind to the ips it is configured to
use.
> >
> > What kind of trouble would you expect ? Can you tell us more ?
> > For a different project, we have just tested drbd between two IP
> > floatting addresses (one for primary, the other one for secondary),
> > and it works pretty well. Should we expect a bad surprise ?
>
> This was only guessing, and I may well be wrong.
> And, the situation is differently, if you use drbd with "floating"
> IPs, as you suggest. (Though I don't see why you would do so.)
The reason is that we currently design a true disaster tolerant solution
with DRBD replicating to a remote site, which supports hot spare secondary:
if either master or secondary fails, a new secondary is picked up,
preferably in the other site if available, else in the only surviving site
in case the remote one is declared down. This implies that both primary and
secondary will 'travel' across several servers. Floatting IP is an elegant
way to simplify the scripts. The solution is under testing now (it is built
for demo, not production yet). I'll let you know more through this notefile
about the results after we complete the tests we are running these days.
Our first comment is that DRBD is a very good and flexible product. Weldone
!
>
> The possible problem I see is when you use a static IP for drbd
> that happens to be in the same "subnet" as one of your floating
> IPs, and somthing decides to take down the latter, it may happen
> that the static ip vanishes, too...
We never met this problem. Is this a bug in ifconfig ? we are not experts in
ifconfig. Since we do not use the static address it might have happen and we
missed it ;-) So, this needs intensive testing.
We use "ifconfig "eth2:1 192.168.1.11 up" and "ifconfig eth2:1 down" which
appeared to be the most deterministic syntax. If a IP specialist reads about
our discussion, please jump in !
>
> I just prefer to have clearly separated floating, system immanent,
> and administrativ IPs.
I agree. We have many floatting IPs in our solution (at least two per DRBD
device), and we must be very careful not to mix them up ;-) So far, in our
tests, site failover based on IP floatting addresses is correctly handled.
>
> Lars Ellenberg
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