[EMAIL PROTECTED] 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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