[Gluster-devel] Replicate/AFR Using Broadcast/Multicast?

[Gordan Bobic]

Craig Carl wrote:
> Gordon -
>     PGM is still experimental so it will be a while before we would 
> consider implementing it,

Just because it isn't officially ratified doesn't mean it's not stable. 
PGM has been stable enough to be implemented in Windows since around 
2002, and there have been libraries for UNIX OS-es for a while, too.

> I would also expect to see network issues as a cluster grows.

Performance reducing as the node count increases isn't seen as a bigger 
issue?

> It would also limit a Gluster cluster to a single 
> broadcast domain. We would have to find a way to manage these 
> challenges, do you have any thoughts?

Why not make the transport switchable between unicast and PGM/broadcast? 
If you need to cross the broadcast domain boundary, use unicast. This 
should probably be selectable per node so that local nodes could be on 
broadcast while remote nodes are on unicast (e.g. for an off-site backup 
node). This isn't not all that big a deal, though, since you can bridge 
networks easily enough - and that would still be more efficient than 
amplifying the write bandwidth usage by a factor of the number of nodes.

Gordan