[Pvfs2-developers] Distribution by hostname

[Rob Ross]

I agree completely with Pete. I think we might consider just adjusting 
the input parameters on the client side to allow for inclusion of the 
list of aliases. There is no reason for these to be stored as part of 
the distribution information on the server, as once the objects are 
created we already know where they are.

We have what, 3 distributions that will need to be adjusted to this new 
scheme? That shouldn't be too bad, and they overall cover a very wide 
range of options.

Regards,

Rob

Pete Wyckoff wrote:
> slang at mcs.anl.gov wrote on Fri, 06 Oct 2006 16:33 -0500:
>> On Oct 6, 2006, at 1:48 PM, Julian Martin Kunkel wrote:
>>> Also it will not
>>> allow to set the servers for all distributions...
>> Yeah I can't imagine wanting to ever do that.  It would mean passing  
>> in a distribution different from the default simple-stripe, as well  
>> as a hint saying you want a specific set of servers in the same  
>> call.  Seems sort of yucky to me.  I'd rather have all the  
>> information about the distribution in the distribution.  You're even  
>> able to use the distribution field in the directory hints structure  
>> to specify per-directory IO server lists.  Not that you would ever  
>> want to do that either...
> 
> I agree with Sam that this is yucky.  I'm hijacking this thread.
> 
> Let's forget about hints for a moment and decide how we want to
> extend the concept of distributions, as seen by users, in such a way
> that they can specify particular IO servers by name.  If this is an
> interface people want, we should design it properly, not just
> implement it with hints because we (might) have them.
> 
> Some issues, please suggest approaches and other issues.  (I'm using
> "name" here to mean host alias.)
> 
> 1.  What kind of control do users want?
> 
>     - all data on one server by name?
>     - arbirtrary control of stripe sizes and host names?
> 
> 2.  New distribution name, or extension to existing ones?
> 
>     - dist-varstrip has a lot of flexibility, but no hostnames
>     - maybe a new "dist-single-host-by-name" is all that is desired
> 
> 3.  Store hostnames in on-disk distribution?
> 
>     - guessing no for the single-stripe distro, but perhaps somebody
>     can really think of a use case for this?
> 
> 4.  User API
> 
>     - through PVFS_dist_create
>     - (please not through both PVFS_dist_create + some hint)
>     - via environment variable too?
> 
> If our design happens to end up as something that would be
> implemented well by hints, then we can think about using them.  For
> now, let's just get the design correct.
> 
> We can come back and argue the merits of a generic hint interface in
> a different thread.
> 
> 		-- Pete
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