[Gluster-devel] volume stanzas for non-existent directories in server volume specification

[John Marshall]

Brandon Lamb wrote:
> Replies are inline, hopefully im right here.... ;-)
>
> <spec example snipped>
>
>   
>> 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?
>>     
>
> I believe you are asking "what happens when you export a non-existant
> directory as a volume?". There should be an error in the logs correct?
>   
>> 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.
>>     
>
> Right, when creating your client volume spec you define which server
> to get the ns volume from. See below. Line 4 defines the remote host
> to get the remote ns sub volume. Line 5 specifies the name of the ns
> subvoluem from the server spec file. However if all of your servers
> are using the same server volume spec file that you included in your
> original post, then to be correct they *should* all have a ns
> directory in order to not give an error. But on your clients, it is
> only going to use the ns directory on the server that you specify in
> the volume definition (line 1).
>
> 1 volume remote-ns
> 2       type protocol/client
> 3       option transport-type tcp/client
> 4       option remote-host host-ns
> 5       option remote-subvolume ns
> 6 end-volume
>   
Right. So, in cases in which a namespace volume is specified, I gather
that I should expect there to be an error logged on all server hosts except
the one exporting the namespace. And, that such errors are _not_ fatal.

To expand, the example server volume specs seem to be minimalistic by
specifying:
-----
volume brick
    type storage/posix
    option directory /data/export
end-volume
-----
This assumes uniformity of the "exported" filesyetem (i.e., /data/export)
and allows a common "volume brick" for the stanza.

My question comes from wanting to export multiple, differently named,
directories from different hosts (assume 1 dir/host). Must I create a
separate server volume spec for each host, or can I simply put all the
information into one spec file and ignore the errors?

Thanks,
John