[DRBD-user] DRBD with more than one secondary node

Mark Watts m.watts at eris.qinetiq.com
Fri Jul 4 13:43:29 CEST 2008

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


DRBD+ Supports 3-way mirroring
	http://www.linbit.com/en/products-services/drbd/drbd-plus/

How you would achieve your goal, I'm not sure; I'm not sure how heartbeat 
would work in this scenario.

Mark.

On Friday 04 July 2008 12:31:00 Hector Blanco wrote:
> Hello.
>
> First of all, I'd like to salute everybody in this list, as this is my
> first message to it. As you might guess, I'm a total newbie here, but
> I'll try to cooperate and help as much as I can.
>
> Now I'd like to raise one question. Basically, it is quite simple:
> Does DRBD support more than two secondary nodes? I guess it doesn't.
> I've never seen a configuration example with more than two nodes
> (primary + secondary) and I thing that (for what I understood in the
> documentation) more than one secondary is not supported because of the
> high network traffic load. But I'm asking because I have seen an email
> (http://osdir.com/ml/linux.highavailability.devel/2006-06/msg00143.html)
> saying that the support of more than two nodes was intended... and
> that was two years ago so maybe I didn't find the right web page :)
>
> Now, if you have more time, I'll try to detail my problem:
>
> I have currently two Xen virtual machines running into a physical
> machine. Each of the virtual machines is running a MySql instance,
> each of which write the data in a drbd partition (thus the Mysql data
> are the same). Over this, I have a Virtual IP controlled by HeartBeat.
> Now, if a machine or a mysqld process fails, all the MySql petitions
> are redirected to the other machine. As you may have foreseen, the
> Drbd resource is controlled by Heartbeat as well. I think this is a
> very typical configuration (I did more or less what is explained here:
> http://marksitblog.blogspot.com/2007/07/mysql-5-high-availability-with-drbd
>-8.html). You should be able to see (if imageshack still keeeps it) a simple
> diagram of what I currently have in the following address:
> http://img388.imageshack.us/img388/6832/pict01tv3.png As I said Both
> machines are Xen Virtual machines but it did't matter much... for the
> moment.
>
> Now I'd like to replicate the structure to another physical machine,
> to have even more security (higher availability) and I don't know
> exactly how I could do it... It would be nice if Drbd could replicate
> in more than two partions. You can see what I want to get in
> http://img379.imageshack.us/img379/2812/pict02hp5.png. What I want is
> tho have everything running (is possible) in monitor01:database01. If
> something in database01 fails, have heartbeat moving everything to
> database02, and keep working connecting to that machine (in a
> transparent way to the MySQL clients), but if monitor01 fails, or
> database01 and database02 fails I have to move to monitor02. And there
> comes my problem. I don't know which would be the best way to have the
> same data in all the database0x machines. I thought in having a DRBD
> unit in monitor01 and monitor02, and then mounting it (via NFS or
> something like that) in the database0x machines. Something like:
> http://img352.imageshack.us/img352/2688/pict03vv6.png but I don't know
> if it is good idea. Could anyone give me a hint, or even a personal
> opinion?
>
> Thank you in advance!!
> _______________________________________________
> drbd-user mailing list
> drbd-user at lists.linbit.com
> http://lists.linbit.com/mailman/listinfo/drbd-user


-- 
Mark Watts BSc RHCE MBCS
Senior Systems Engineer
QinetiQ Applied Technologies
GPG Key: http://www.linux-corner.info/mwatts.gpg
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