[DRBD-user] dual primary DRBD, iSCSI and multipath possible?

Markus Hochholdinger Markus at hochholdinger.net
Mon Oct 4 21:56:12 CEST 2010


Hello,

Am 15.03.2010 um 15:47 Uhr schrieb Olivier LAMBERT 
<lambert.olivier at gmail.com>:
> :D
> That's I'm using right now, but it's for Xen on the top.
> I think this is the only good reason to do that.

I'm also in the process of evaluating this (for a xen setup).

My setup would be:
On two nodes drbd with active/active (so xen live migration would work). On 
each node export the drbd device with iscsi.
On each other node import the iscsi devices of both drbd nodes and put 
multipath over it.

The tricky part now is how to handle failures. With this setup it is possible 
that multipath switches between both drbd nodes. If we do this more than once 
while we have a split brain, this would destroy our data!

So the goal would be to develope a good multipath strategy.

How do you do this?


My idea is to say multipath to stick to one path and only switch on an error. 
Also you have to say multipath to NOT recover faulty paths autmatically to 
prevent data loss in a split brain situation.

After a failure someone has to manually recover the drbd active/active devices 
(if not done autmatically) and then (and ONLY then) to recover the faulty 
path for multipath. And this on all nodes...

Or do I miss some features of drbd which could help here?


> On Mon, Mar 15, 2010 at 3:15 PM, Florian Haas <florian.haas at linbit.com> 
wrote:
> > I think there are cheaper ways to go insane.
> >
> > Florian
> >
> > On 03/15/2010 12:26 PM, Michael Schwartzkopff wrote:
> >> Hi,
> >>
> >> I wanted to know if a dual primary DRBD setup, exporting the block
> >> devices  as iSCSI targets and multipathing on the initiator side is
> >> possible and advisable.
> >>
> >> Thanks for any enlightening answers.
> >>
> >> Greetings,
> >
> > _______________________________________________
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>
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-- 
greetings

eMHa
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