[Linux-cluster] how to GFS mirroring? GFS+CLVM+GNBD? GFS+cmirror? GFS+DRBD? GFS+ddraid?

[andremachado]

Hello,
I am trying to find some configuration to mirror GFS, for a no single point of failure in a very simple department small cluster.
Using 3 simple identical machines (Debian 4.0 Etch), with a single ide each, I found an interesting article [0] that told it is feasible.
At some old archived messages of this list, some told that this approach was not working.
cmirror was removed from the cvs tree [2], but as recently as March 2007 [1] someone was trying it.
ddraid [4] was included [5] and then removed from source tree too (for building deb packages). 
At some archived messages, someone suggested Open Sharedroot [6].
I throughly read cluster docs [8], except the LVS part. (the extensive docs lack some cluster.conf logic structure examples and excessively focus on gui wizard handholding)
drbd *seems* not being exactly what i want to accomplish (limited 2 nodes, one node write, etc)

I was guessing that by may 2007, GFS+CLVM+GNBD could accomplish this, while cmirror or ddraid are not back in tree.
Ian Blenke tried something similar [9], but settled using Xen and its parameters for mirroring.
VERY interesting, but it is not exactly what I am trying.
( Maybe I could setup a Xen hosted server for serving the GFS files...)

Using GNBD for exporting (clvm logical volume or raw /dev/hdx partition?) and clvm for mirroring ( -m 1) could be used with GFS?
I am pretending to use 2 machines for mirroring (no third dedicated log volume) and exporting GNBD to the third machine, being a GFS server.

A fourth different configuration machine will be the GFS client for writing at GFS.
Already got GFS working with 2 nodes cluster in Debian 4.0 Etch with some patching [10].

Do you have any suggestions or guidance about how to accomplish this simple GFS mirroring to avoid single point of failure?

Regards.
Andre Felipe Machado
http://www.techforce.com.br



[0] http://www.redhat.com/magazine/008jun05/features/gfs/#fig-mirroring
[1] http://www.redhat.com/archives/linux-cluster/2007-March/msg00071.html
[2] http://sources.redhat.com/cgi-bin/cvsweb.cgi/cluster/?cvsroot=cluster
[3] http://www.redhat.com/archives/linux-cluster/2007-March/msg00071.html
[4] http://sourceware.org/cluster/ddraid/
[5] http://www.redhat.com/archives/linux-cluster/2005-March/msg00115.html
[6] http://www.open-sharedroot.org/
[7] http://www.drbd.org
[8] http://www.redhat.com/docs/manuals/csgfs/
[9] http://ian.blenke.com/projects/xen/cluster/buildingxenclusterstep9.html
[10] http://lists.alioth.debian.org/pipermail/utnubu-discuss/2007-May/000574.html