[Linux-cluster] GNBD Configuration Question

Benjamin Marzinski bmarzins at redhat.com
Mon Feb 13 20:02:59 UTC 2006

On Fri, Feb 10, 2006 at 01:03:36PM -0600, Curt Moore wrote:
> Hello all.
> I've been experimenting with RH Cluster Suite and GFS and have come
> upon a few questions which I hope the list will be able to help. 
> Kudos to all of the developers, RHCS and GFS are really cool!
> To my question, I'm trying to setup a storage network with GFS and
> GNBD using a 3 layered approach as shown in Figure 5 in the following
> link:
> http://www.redhat.com/magazine/008jun05/features/gfs/#fig=multipath
> and also here:
> http://www.redhat.com/docs/manuals/csgfs/browse/rh-gfs-en/s1-ov-perform.html#S2-OV-MODPRICE
> Obviously, the intent is to eliminate any SPOF for the storage network.
> For the sake of example, let's say that I have 2 GNBD servers
> connected directly to the SAN, snode001 and snode002.
> If I export the the same SAN block device from these 2 GNBD servers
> for load sharing purposes and snode001 fails, how do the GNBD clients
> importing that block device from snode001 know that they can also find
> that block device on snode002?  Is this somehow handled at a lower
> level by configuring a resource within the RH Cluster Suite?
> I've scoured the list archives and found the following example, using
> multipath, which seems to come very close:
> http://www.redhat.com/archives/linux-cluster/2005-April/msg00065.html
> However, the documentation states that multipath GNBD cannot be used
> with GFS 6.1:
> http://www.redhat.com/docs/manuals/csgfs/browse/rh-gfs-en/ch-gnbd.html
> Is there another way of accomplishing this without using multipath or
> am I misunderstanding the concept of how multipath is utilized in this
> setup?

The only way for a gnbd client to access the same data served up by two gnbd
servers is to use some multipath implementation. Currently there is no
mulipath implementation that supports gnbd devicse. sorry.


> Any feedback would be appreciated.
> Thanks!
> -Curt
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