Open Stack

On 02/04/2015 03:04 AM, Li, Chen wrote:
>
> Hi list,
>
> For generic driver, there is a flag named 
> “connect_share_server_to_tenant_network” in 
> manila/share/drivers/service_instance.py.
>
> When it set to True, share-server(nova instance) would be created 
> directly on the “share-network”.
>
> When it set to False, the subnet within share-network must connected 
> to a router, and then manila would create its own subnet and connect 
> to the router too, and start share-server in manila’s subnet.
>
> Based on 
> https://wiki.openstack.org/wiki/Manila/Networking#Gateway_Mediated, I 
> assume the difference here is L2 vs L3 connectivity.
>
> But, I wander whether there are some other reasons for generic driver 
> to support this flag.
>
> So, my question here is:
>
>         As an cloud admin, what I need to consider to help me figure 
> out what value I should set for this flag ?
>

L3 connectivity tends to be dramatically more efficient in a larger 
cloud because it limits the size of the broadcast domains. If you try to 
use L2 connectivity between the share server and all its clients, and 
any of those machines are separately in the physical world (separate 
racks, separate aisles, separate datacenters) then all your ARP traffic, 
etc, is traversing backbone links.

The only benefit to L2 connectivity that I'm aware of is a potential 
performance improvement by removing the (virtual) router as a bottleneck.

-Ben Swartzlander


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