[CentOS] Xen, GFS, GNBD and DRBD?

[Marc Grimme]

Hi Tom,
On Wednesday 02 January 2008 23:44:19 Tom Lanyon wrote:
> Hi all,
>
> We're looking at deploying a small Xen cluster to run some of our
> smaller applications. I'm curious to get the lists opinions and advice
> on what's needed.
I'm not the biggest fan of DRBD with Xen and everything but it's for a "small" 
Xen cluster isn't it ;-) . In my opinion it brings way to much complexity in 
a concept that should always stay as simple as possible.
>
> The plan at the moment is to have two or three servers running as the
> Xen dom0 hosts and two servers running as storage servers. As we're
> trying to do this on a small scale, there is no means to hook the
> system into our SAN, so the storage servers do not have a shared
> storage subsystem.
>
> Is it possible to run DRBD on the two storage servers and then export
> the block devices over the network to the xen hosts? Ideally the goal
> is to have the effect of shared storage on the xen hosts so that
> domains can be migrated between them in case one server needs to go
> offline. Do I run GFS on top of the DRBD mirrored device, exported via
> GNBD to the xen hosts; or the other way around, using GNBD to export
> the DRBD mirrored device and then GFS running on the xen hosts?
>
> Is this possible; is there an easier/simpler/better way to do it?
For DRBD as base for GFS you might want to have a look at
http://gfs.wikidev.net/DRBD_Cookbook

I didn't test it but it might be what you are looking for.

When thinking about GNBD you could also think about iSCSI (as already stated) 
as it is a standard. Make it highly available move it onto some other two 
nodes and there you go. But still there you'll need shared storage. How about 
extending your thoughts also onto NFS. Again you'll have to make it highly 
available which results in shared storage or DRBD.

BTW: Don't make your *small* cluster to complex to manage. ;-)

Have fun
Marc.

-- 
Gruss / Regards,

Marc Grimme
http://www.atix.de/               http://www.open-sharedroot.org/