[DRBD-user] three node backup setup without public/internal IP address

Sven Duscha sven.duscha at helmholtz-muenchen.de
Thu May 8 21:12:29 CEST 2014

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Hi Lars,

On 07/05/14 12:54, Lars Ellenberg wrote:
> On Tue, May 06, 2014 at 02:02:14PM +0200, Sven Duscha wrote:
>> I am trying to set up a three-way redundant DRBD. The way I understand
>> it, this is only possible as a primary/secondary-pair with an "external"
>> stacked-on-top backup.
>> resource r0 {
>>         address;
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>> The problem is that my third node is within the same IP range as the
>> other two.
> That is a common setup.

I would thought so.

>> Therefore is no dedicated second IP interface with an external IP.
> You don't need a second interface,
> and you don't need an external IP either.
>> I then get an error message about a doubly assigned IP address.
> No. You get a message about doubly assigned (IP address : port) tuple.
> If you cannot use a dedicated "service" IP for the stacked DRBD,
> at least use a different port.

Thanks! That did the trick.

> What you *should* do is have a service IP (it's ok if that is in the
> same range), and put that as secondary IP on the interface,
> on the node that is supposed to be primary.
> That way, the third node can connect to the same (service) IP,
> regardless of which node of the "primary cluster" is currently active.
> But that is not required, you could use the node IPs as well.
> Though reconnect to the third node after switchovers on the main cluster
> will be cumbersome then.

This then has to be done with Pacemaker/Heartbeat? I'll have to read up
on those then to get failover behaviour set up.

>> Is the a way to create a such setup within the same cluster? I read up a
>> bit on the Pacemaker section which proposes a three-way and four-way
>> method, though, also intended to be "external". Do I need the commercial
>> DRBD-Proxy for the Pacemaker-setup or is this optional?
> DRBD Proxy is independent from "third node" setups,
> though typically they are used together.
> DRBD Proxy helps in masking latency peaks caused by write bursts,
> if the replication link is "high latency low throughput",
> where both "high latency" and "low throughput" is obviously relative,
> and range from 300ms and 10 MBit (for some customers) to 10ms and 10Gbit
> (for other customers), and are to be compared with the typical
> performance characteristics of the primary system.

Ok, thanks for the clarification.



Sven Duscha, M.Sc.
Institute of Bioinformatics and System Biology
Phone: +49-89-3187-1157
Fax: +49-89-3187-3585
mailto:sven.duscha at helmholtz-muenchen.de

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