scaling of shared storage

[Jan Hudec]

On Mon, Feb 06, 2006 at 11:13:56 -0500, Aaron Bentley wrote:
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> Jan Hudec wrote:
> >>I'm not sure about this; it seems like a half-measure.  There's nothing
> >>preventing bad scaling behaviour *within a project* this way.  So I
> >>think we may want to split inventories further, perhaps every 100
> >>revisions, or every x bytes, or something.
> > 
> > 
> > The question is whether /that/ actually helps anything. 
> 
> I think that it would help on a project with tens of thousands of
> revisions.  You'd split at annotations, of course.

Yes, makes sense. Is there a way to add a full-text into the knit now
and then?

Well, projects with tens of thousands of revisions would probably want
to have an option to only carry revisions younger than something over to
a branch. Darcs can do something like that.

> > That is how much
> > it helps after knits are in. On the other hand splitting inventory
> > per-directory certainly does help anything (most projects contain
> > directories they touch rarely) 
> 
> So what about the projects that don't contain directories they touch
> rarely?  Depending on user behaviour to ensure good scaling seems
> dubious to me.

It does not really improve scaling over the number of revisions. Only
the constant factor and that is dependent on the user behaviour.

> > and it would make branching a subtree
> > some bits simpler. Which I think would be an important feature - you may
> > often realize you want to split out some part as library only after a
> > while when it grows to substantial size.
> 
> You'll have to clarify how that would make it simpler.

You would not have to process the inventories. Just select the right
ones. Though you'd still have to process revisions, so it probably does
not help all that much.

> >>This implies that the tree root is added in the first revision, and that
> >>is okay with me.  I will happily make whatever changes are needed to
> >>avoid actually creating / deleting the root directory.  (Though the way
> >>branch creation works, I don't think we need to do that.  Probably we
> >>just need to make it illegal to revert to -r 0)
> > 
> > 
> > Maybe not even that. When you add a file, all it's parent directories
> > need to get added automatically -- which includes root. revert -r 0
> > deletes the root... you get a new project when you add it again, but
> > I think that's OK -- while the operation is legal, it's hardly sensible.
> 
> I don't believe it is possible or desirable to delete the CWD.

Delete in the sense remove from version control. Not physically, of
course.

-- 
						 Jan 'Bulb' Hudec <bulb at ucw.cz>
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