[Linux-cluster] GNBD import mirroring?

Benjamin Marzinski bmarzins at redhat.com
Mon Dec 12 18:42:33 UTC 2005

On Mon, Dec 12, 2005 at 11:22:25AM -0600, Brenton Rothchild wrote:
> Hi all,
> I was thinking about trying to set up a test cluster
> according to the figure in
> http://www.redhat.com/docs/manuals/csgfs/admin-guide/s1-ov-perform.html#S2-OV-ECONOMY
> but I see a post from Benjamin Marzinski that this is a
> marketing fluke and isn't possible?
> (http://www.redhat.com/archives/linux-cluster/2005-February/msg00049.html)

The documentation has been corrected. The picture, as is stands now is a valid
configuration. previously, it looked like this

----------   -----------   -----------
|        |   |         |   |         |   GNBD servers
----------   -----------   -----------
    /\           /\             /\
   A  B'        B  C'          C  A'

Meaning that you were doing mirroring on the gnbd clients. This is untested
and unsupported.
> Is that true, or this possible?  I'd like to make use of two GNBD
> export servers that I could RAID 1+0 on the GNBD import nodes
> to get a network mirror plus resizeable GFS parition...
> if that's even possible.

I still believe that it's possible that someone with a bit of time and
understanding could hack some stuff and get GNBD running on top of DRBD.
I'm pretty sure I explained how I thought that this could be done on a past
post, which I can't locate now.  I would never do this on a production setup
unless you really knew what you would doing, and were willing to support it
yourself, and tested it like mad first.

The problem with mirroring is that if a machine dies, it may have successfully
written to one server and not the other.  Now your mirror is out of sync, and
a non-cluster aware mirror setup would never know.  The non-painful solution
is to use cluster mirroring, which will be available through CLVM soonish.


> If anyone could tell me if I'm barking up the wrong tree on this,
> I'd appreciate it!
> Thanks,
> -Brenton Rothchild
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