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Re: Quota definitions
On Tue, Jul 28, 2009 at 08:53:41PM +0200, Manuel Bouyer wrote:
> > > I would go with a new format. The current format is a table indexed
> > > by uid or gid. If you use large uid you get a very large sparse file.
> > > A different indexing scheme is needed.
> > I'm not convinced. Linux did this and I don't really see the point -
> > instead of reusing the FS's tree structure for managing a sparse file,
> > they added another layer of tree structure, which buys complexity and
> > recovery problems and not a whole lot else.
> This huge sparse file cause issues too; some tools don't deal properly
> with sparse files. Now, if the file is hidden most of these issues go away.
Such tools should be fixed :-)
Of course, in any new implementation the quota file should be hidden,
but I think we ought to keep the existing FFS quota representation for
FFS to retain interoperability.
> > Because uids mostly tend to come in contiguous sequences, I'm not
> > convinced that in practice one will tend to see quota files with lots
> > of blocks that each hold the info for one user and are otherwise
> > empty. Except maybe on large installations with lots of uids and lots
> > of uid turnover, but even then I expect a much bigger problem is that
> > quota records for removed users probably aren't ever G/C'd.
> Yes, that's another issue. The uid turnover also leads to a sparse uid
Right. Changing the data structures around won't help much with that
David A. Holland
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