[DRBD-user] 3-node active/active/active config?

Jiann-Ming Su sujiannming at gmail.com
Wed Nov 18 05:30:04 CET 2009


On Tue, Nov 17, 2009 at 12:50 PM, Lars Ellenberg
<lars.ellenberg at linbit.com> wrote:
>
> No. You did not understand.
>
> It is not a question of performance.
> Or whether a write reached all *nodes*.
>
> In your setup, it is technically *impossible*
> for a write to reach all lower level *disks*.
>

Can you give a brief explanation of why that is the case?

> again, your fancy cool and whatever setup won't work.
> DO NOT DO THIS.
>


Is the problem the dual path?  What if a single path was used in some
stacked configuration where a drbd is used as a backing device for
another drbd share?


> A sure way to data corruption.
>
> Got me this time?
>
>  ;)
>
> So by all means: use one iSCSI on DRBD cluster,
> and have any number of ocfs2 clients via iSCSI.
> Or double check if NFS can do the trick for you.
>

We have three geographically independent locations that have to share
data, but still remain independent.  iSCSI is an interesting idea
since it exposes a block device.  But, I could ask the same silly
question I'm asking now about drbd:  is it possible to come up with
some clever way to do a 3-node config?  Or, will it run into the same
technical limitations that you say drbd has?

I'm almost better off synchronizing with manually with rsync than
using iSCSI or NFS in the more conventional sense.  I mean, currently,
we do a pretty simple two node DRBD config, but it'd be nice to add in
a third.

> again, your fancy cool and whatever setup won't work.
> DO NOT DO THIS.
>

The question really is whether this is a desirable configuration?  If
so, what technical limitations have to be overcome to make something
like this work.

-- 
Jiann-Ming Su
"I have to decide between two equally frightening options.
 If I wanted to do that, I'd vote." --Duckman
"The system's broke, Hank.  The election baby has peed in
the bath water.  You got to throw 'em both out."  --Dale Gribble
"Those who vote decide nothing.
Those who count the votes decide everything.”  --Joseph Stalin


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