volume stanzas for non-existent directories in server volume specification

[John Marshall <John.Marshall@xxxxxxxx>]

Hi,

Given the following server volume specification:
-----

volume a
	type storage/posix
	option directory /data/a
end-volume

volume b
	type storage/posix
	option directory /data/b
end-volume

volume ns
	type storage/posix
	option directory /data/ns
end-volume

volume server
	type protocol/server
	option transport-type tcp/server
	option auth.ip.a.allow *
	option auth.ip.b.allow *
	option auth.ip.ns.allow *
	subvolumes a b ns
end-volume

-----
and the following client volume specification:
-----

volume remote-a
	type protocol/client
	option transport-type tcp/client
	option remote-host host-a
	option remote-subvolume a
end-volume

volume remote-b
	type protocol/client
	option transport-type tcp/client
	option remote-host host-b
	option remote-subvolume b
end-volume

volume remote-ns
	type protocol/client
	option transport-type tcp/client
	option remote-host host-ns
	option remote-subvolume ns
end-volume

volume unify
	type cluster/unify
	option scheduler rr
	option namespace remote-ns
	subvolumes remote-a remote-b remote-ns
end-volume

-----
Note: it is assumed that host-a:/data/a, host-b:/data/b,
host-ns:/data/ns exist.

Q. Does gluster have a problem with server spec volumes which do
not exist on a given host? From the "Aggregating Three Storage
Servers with Unify" example is does not seem like it would, since
the namespace volume is _not_ on all nodes.

Q. How do the gluster servers know which directories to "export"
from each host? Is it based on requests from the client? I.e., The
server does not care until/unless a client asks?

Thanks,
John