[Sheepdog] VMs outside cluster - HA

[MORITA Kazutaka]

Hi,

Thanks for your testing!

At Sat, 08 Jan 2011 22:23:08 +0100,
Christof Egner wrote:
> 
> Hi,
> 
> I'm currently testing Sheepdog with VMs running outside the cluster. The 
> gateway node used to connect to the cluster is a SPOF in this scenario. 
> I was wondering if it could be solved by accessing the cluster through 
> load balancers (virtual IP address)?

Each VM cannot send I/O requests through multiple gateway nodes
because of Sheepdog design limitations.  So adding load balancers
doesn't solve this problem; the gateway node is still SPOF.  I think
the best way is that after the gateway node is down, the VM uses
another gateway node.

> 
> Does it make sense to balance new connections over the cluster or is it 
> better to select one active master node?

If each VM uses only one gateway at the same time, it is no problem to
use multiple gateways with multiple VMs for load balancing.  So it
makes sense to balance new connections over the cluster.

> 
> What happens if a gateway node fails. Connected clients would be 
> redirected to other nodes. Does it have any impact to the clients?

The clients cannot send I/O requests to Sheepdog anymore.  This should
be fixed ASAP.

> 
> What happens if additional nodes join the cluster: does Sheepdog 
> re-balance existing data objects?

Yes, exactly.


Thanks,

Kazutaka