[Linux-cluster] GNBD vs DRBD to mirror two disks via the network

[Bryn M. Reeves]

On Mon, 2009-07-13 at 15:40 +0100, Bushby, Bruce (London)(c) wrote:
>  
> Greetings!
>  
> I'm hoping a member could assist me in clearing up some understanding
> I appear to be missing when it comes to GNBD.
>  
> Today I clustered two vmware machines (active/passive shared nothing)
> and then configure GNBD....thats when I noticed it
> wants to "export" a device from one node and "import" the device on
> the other node...which I did and it all works....but that is
> not what I was after.
>  
> Can GNBD be configured to keep two disks on different systems in sync
> using both synchronous and asynchronous write options?

No. GNBD is just a cluster-aware network block device (i.e. it
implements fencing so that we can cut off a failing node from the shared
storage).

It's only useful if you want shared storage for e.g. GFS but don't have
access to hardware shared storage resources (or only have shared storage
hardware on a subset of nodes and want to spread that out to more nodes
using IP).

Regards,
Bryn.